Intel Agilex Clocking and PLL User Guide

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UG-20216 | 2021.09.21

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Intel® Quartus® Prime Design Suite 20.3

1. Intel Agilex Clocking and PLL Overview

1.1. Clock Networks Overview

Intel^® Agilex™ devices contain dedicated resources for distributing signals throughout the fabric. Typically, you use these resources for clock signals and other signals with low-skew requirements. In Intel^® Agilex™ devices, these resources are implemented as a programmable clock routing network, which allows for the implementation of various low-skew clock trees.

1.2. PLLs Overview

Phase-locked loops (PLLs) provide robust clock management and synthesis for device clock management, external system clock management, and high-speed I/O interfaces.

The Intel^® Agilex™ device family contains the following I/O PLLs for core applications. The I/O PLLs can only function as integer PLLs.

Fabric-feeding I/O PLLs—three C counter outputs available and do not support PLL cascading
I/O bank I/O PLLs—seven C counter outputs available and support PLL cascading

The I/O PLLs are located adjacent to the hard memory controllers and LVDS serializer/deserializer (SERDES) blocks in the I/O banks. Each I/O bank contains two I/O bank I/O PLLs and one fabric-feeding I/O PLL.

2. Intel Agilex Clocking and PLL Architecture and Features

2.1. Clock Networks Architecture and Features

2.1.1. Clock Network Architecture

Each Intel^® Agilex™ device is divided into a number of evenly sized clock sectors.

Figure 1. Clock Sector Floorplan for Intel^® Agilex™ DevicesThis figure shows an example of the clock sectors in an Intel^® Agilex™ device, which is implemented as an array of sectors—5 rows and 6 columns in this example. I/O banks are at the top and bottom of the Intel^® Agilex™ device.

2.1.1.1. Clock Network Hierarchy

The Intel^® Agilex™ clock network is organized in a hierarchy with 3 levels.

Figure 2. Clock Network Hierarchy

2.1.1.2. Clock Sectors

Each clock sector has a dedicated sector clock (SCLK) network and a row clock network that can be accessed by the programmable clock routing. On each side of the clock sector, there is a channel that contains 64 unidirectional wires in bidirectional pairs, where only one wire in each pair can be used at one time. At each corner, there is a set of programmable clock switch multiplexers that can route between these clock wires.

A signal on a vertical clock wire can enter the sector to its left or right via clock tap multiplexers. The clock tap multiplexer drives a sector clock, which distributes the signal to each row in the clock sector. In each row, there are six row clock resources that route to all core functional blocks, PLLs, and I/O interfaces in the sector, and to adjacent transceivers.

Figure 3. Dedicated Clock Resources Within a Clock Sector

2.1.1.3. Programmable Clock Routing

The Intel^® Quartus^® Prime software automatically configures the clock switch multiplexer, clock tap multiplexer, SCLK multiplexer, and row clock multiplexers to generate skew-balanced clock trees. The resulting routing path distributes the signal from the clock source to all target destinations in one or more clock sectors.

The Intel^® Quartus^® Prime software creates efficiently balanced clock trees of various sizes, ranging from a single clock sector to the entire device, as shown in the following figure. By default, the Intel^® Quartus^® Prime software automatically determines the size and location of the clock tree. Alternatively, you can directly constrain the clock tree size and location by using either a Clock Region Assignment or Logic Lock Regions.

The total insertion delay for the clock network depends on the number of clock resources needed to implement the clock tree, increasing with the distance of the furthest clock destination from the signal source. As delay increases, the worst-case skew for crossing clock networks using different clock tree branches grows, potentially degrading the maximum performance. For very high-speed clock signals, it is advantageous to follow these guidelines:

Reduce the number of clock networks driven, which reduces the clock skew.
Reduce the distance between the clock source and the furthest destination, which reduces both clock skew and total clock insertion delay.

Figure 4. Examples of Clock Networks Sizes Using Intel^® Agilex™ Device Programmable Clock Routing

2.1.2. Clock Resources

Table 1. Programmable Clock Routing Resources for Intel^® Agilex™ Devices
Number of Resources Available	Source of Clock Resource
32 pairs of unidirectional programmable clock routing at the boundary of each clock sector	For transceiver bank: Physical medium attachment (PMA) and physical coding sublayer (PCS) TX and RX clocks per channel PMA and PCS TX and RX divide clocks per channel Hard IP core clock output signals `REFCLK` pins Core signals ¹ For I/O bank: I/O PLL `C` counter outputs I/O PLL `M` counter outputs for feedback Phase aligner counter outputs Dynamic phase alignment (DPA) clock output Clock input pins Core signals ¹

For more information about the clock input pins connections, refer to the pin connection guidelines.

¹ Core signals drive directly to programmable clock routing through clock switch multiplexers in the clock sectors instead of the periphery DCM block.

2.1.3. Clock Control Features

The following figure shows a high-level description of the Intel^® Agilex™ clock control features—clock gating and clock divider. The clock from the I/O PLL output can be gated dynamically. These clock signals along with other clock sources go to the periphery distributed clock multiplexer (DCM). In the periphery DCM, the clock signal can either pass straight through, be gated by the root clock gate, or be divided by the clock divider.

The Intel^® Quartus^® Prime software routes the clock signal on the programmable clock routing to reach each clock sector. The clock signal can be gated in each sector by the SCLK gates. The clock enters the SCLK network followed by the row clock network, and eventually reaches the registers in the core. The LAB registers have a built-in functional clock enable feature, as shown in the following figure.

Figure 5. Clock Gating and Clock Divider in Intel^® Agilex™ Clock Network

2.1.3.1. Clock Gating

2.1.3.1.1. Root Clock Gate

There is one root clock gate per I/O bank and transceiver bank. This gate is a part of the periphery DCM.

The Intel^® Agilex™ root clock gate is intended for limited clock gating scenarios where high insertion delay can be tolerated. When you use a root clock gate, set multicycle of several clock cycles between the generation of the clock gating signal in the core and the gated clock in the periphery to meet the timing requirement. For high frequency clocks that require single-cycle gating, use sector clock gates.

2.1.3.1.2. Sector Clock Gate

Every sector of the device has 32 SCLKs. Each SCLK has a clock gate and a path that bypasses the clock gate. The SCLK gates are controlled by clock enable inputs from the core logic. The Intel^® Quartus^® Prime software can route up to eight unique clock enable signals to the 32 SCLKs in a sector.

Intel recommends using the clock gate with a negative latch to provide glitch free gating on the output clock signal (outclk). The clock gate captures the enable signal (clkena) on the next rising edge of the input clock signal (inclk). The following timing diagram shows the relationship of the outclk with respect to inclk and clkena.

Figure 6. Clock Gating Timing Diagram

The clock signal going into the SCLK network in a sector can only reach the core logic in that sector. When you instantiate a SCLK gate in your design, the Intel^® Quartus^® Prime software automatically duplicates the SCLK gate to create a clock gate in every sector to which the clock signal is routed.

The SCLK gate is suitable for cycle-specific clock gating for high-frequency clocks. The timing of the enable path to the SCLK gate is analyzed by the Intel^® Quartus^® Prime Timing Analyzer.

2.1.3.1.3. I/O PLL Clock Gate

You can dynamically gate each output counter of the Intel^® Agilex™ I/O PLL. This I/O PLL clock gate provides a useful alternative to the root clock gate. The root clock gate can gate only 1 of 7 output counters.

However, the I/O PLL clock gate is not cycle-specific. When you use the I/O PLL clock gate, expect a delay of several clock cycles between the assertion or deassertion of the clock gate and the corresponding change to the clock signal. The number of delay cycles is non-deterministic because the enable signal must be synchronized into the clock domain of the output clock, ensuring a glitch-free gate.

2.1.3.1.4. LAB Clock Gate

The Intel^® Agilex™ LAB register has built-in clock gating functionality. The register clock enable mechanism is a hardened data feedback, as shown in the Clock Gating and Clock Divider in Intel^® Agilex™ Clock Network diagram. The LAB clock gate offers no associated power savings because this is a purely functional clock enable.

The Intel^® Quartus^® Prime Analysis & Synthesis stage of the Compiler infers a LAB clock gate from a behavioral description of clock gating in the register transfer level (RTL). If you want a physical clock gate, you must instantiate it explicitly.

2.1.3.2. Clock Divider

There is one clock divider per I/O bank and transceiver bank. The clock divider is a part of the periphery DCM block and is located close to the root clock gate. The outputs of the clock divider cannot be gated by the root clock gate in the same periphery DCM block. However, this limitation does not apply to the SCLK gate. The clock divider output in the periphery DCM block can drive a SCLK gate after going through the programmable clock routing.

The clock divider has three outputs as follows:

First output—passes through the input clock.
Second output—divides the input clock by two.
Third output—divides the input clock by four.

These three clock outputs are edge-aligned at the output of the clock divider.

Figure 7. Clock Divider Timing Diagram

2.2. PLLs Architecture and Features

2.2.1. PLL Features

Table 2. PLL Features in Intel^® Agilex™ Devices—Preliminary
Feature	I/O Bank I/O PLL	Fabric-Feeding I/O PLL
Integer PLL	Yes	Yes
Number of `C` output counter	7	3
`M` counter divide factor range	4 to 160	4 to 160
`N` counter divide factor range	1 to 110	1 to 110
`C` counter divide factor range	1 to 512	1 to 512
Dedicated external clock outputs ²	Yes	—
Dedicated clock input pins	Yes	Yes
External feedback input pin	Yes	—
Source synchronous compensation ³	Yes	Yes
Direct compensation	Yes	Yes
Normal compensation ³	Yes	Yes
Zero-delay buffer compensation	Yes	—
External feedback compensation	Yes	—
LVDS compensation	Yes	—
Voltage-controlled oscillator (VCO) output drives the DPA clock	Yes	—
Phase shift resolution ⁴	78.125 ps	78.125 ps
Programmable duty cycle	Yes	Yes
Power down mode	Yes	Yes
Bandwidth setting	Low, medium, and high	Medium and high
Spread-spectrum input clock tracking ⁵	Yes	Yes

Table 3. Spread-Spectrum Input Clocking Supported Profile
Spread-Spectrum Clocking Parameter	Setting
Modulation frequency	200 kHz
Center or down spread	Down spread
Frequency deviation	±1%
Modulation profile	Triangle

² For dedicated external clock outputs, you must enable access to external clock output port through IOPLL Intel^® FPGA IP core. There are 2 dedicated external clock output available for each I/O bank I/O PLL.

³ Non-dedicated feedback path option is available for this compensation mode.

⁴ The smallest phase shift is determined by the VCO period divided by eight. For degree increments, the Intel^® Agilex™ device can shift all output frequencies in increments of at least 45°. Smaller degree increments are possible depending on the frequency and divide parameters.

⁵ Provided that input clock jitter is within the input jitter tolerance specifications. Intel recommends that the spread-spectrum support profile is down spread, ±0.5% and F_mod = 200 kHz.

2.2.2. PLL Usage

I/O bank I/O PLLs are optimized for use with memory interfaces and LVDS SERDES. You can use both the I/O bank I/O PLLs and fabric-feeding I/O PLLs to:

Reduce the number of required oscillators on the board
Reduce the clock pins used in the FPGA by synthesizing multiple clock frequencies from a single reference clock source
Simplify the design of external memory interfaces and high-speed LVDS interfaces
Ease timing closure because the I/O PLLs are tightly coupled with the I/Os
Compensate for clock network delay
Zero delay buffering

2.2.3. PLL Locations

Figure 8. I/O PLL Locations in I/O Bank

Within an I/O bank, the top sub-bank is placed near the edge of the die, while the bottom sub-bank is placed near the FPGA core.

If one of the sub-banks is not available in the I/O bank, the dedicated clock input and clock output pins for the I/O PLL located in this unbonded sub-bank are unavailable. However, you can still use the I/O PLL in the following scenarios by ensuring the VCCPT is powered up:

PLL cascading and reconfiguration are supported.
You may use any available regular I/O pins as clock input and clock output pins for this I/O bank I/O PLL.

If one of the sub-banks is not available in the I/O bank, the fabric-feeding I/O PLL in this I/O bank has only one pair of dedicated clock input pins which is from the available sub-bank. Reconfiguration is supported by this fabric-feeding I/O PLL.

2.2.4. PLL Architecture

Figure 9. I/O Bank I/O PLL High-Level Block Diagram for Intel^® Agilex™ Devices

Figure 10. Fabric-Feeding I/O PLL High-Level Block Diagram for Intel^® Agilex™ Devices

Note: The dedicated clock inputs can feed only one PLL via the dedicated clock path. To feed the second PLL, the clock must be routed onto a global clock network.

2.2.5. PLL Control Signals

You can use the reset signal to control PLL operation and resynchronization, and use the locked signal to observe the status of the PLL.

2.2.5.1. Reset

The reset signal port of the IP core for I/O PLL is reset.

The reset signal is the reset or resynchronization input for each I/O PLL. The device input pins or internal logic can drive these input signals.

When the reset signal is driven high, the I/O PLL counters reset, clearing the I/O PLL output and placing the I/O PLL out-of-lock. The VCO is then set back to its nominal setting. When the reset signal is driven low again, the I/O PLL resynchronizes to its input clock source as it re-locks.

You must assert the reset signal every time the I/O PLL loses lock to guarantee the correct phase relationship between the I/O PLL input and output clocks. You can set up the I/O PLL to automatically reset (self-reset) after a loss-of-lock condition using the Intel^® Quartus^® Prime parameter editor.

You must include the reset signal if either of the following conditions is true:

I/O PLL reconfiguration or clock switchover is enabled in the design.
Phase relationships between the I/O PLL input and output clocks must be maintained after a loss-of-lock condition.

Note:

Reset the I/O PLL after the input clock is stable and within specifications, even when the self-reset feature is enabled, if either one of the following conditions occur:

The input clock to the I/O PLL is not toggling or is unstable when the FPGA transitions into user mode.
The I/O PLL cannot lock to the reference clock after reconfiguring the I/O PLL.

2.2.5.2. Locked

The locked signal port of the IP core for the I/O PLL is locked.

The lock detection circuit provides a signal to the core logic. The signal indicates when the feedback clock locks onto the reference clock both in phase and frequency.

PLL loses lock if the input reference clock stops toggling. When PLL loses lock, the output of the PLL starts drifting out of the desired frequency. The downstream logic must be held inactive when PLL has lost lock.

2.2.6. PLL Feedback Modes

PLL feedback modes compensate for clock network delays to align the rising edge of the output clock with the rising edge of the PLL's reference clock. Select the appropriate type of compensation for the timing critical clock path in your design.

PLL compensation is not always needed. Configure a PLL in direct (no compensation) mode unless you need compensation. Direct mode provides the best PLL jitter performance and avoids expending compensation clocking resources unnecessarily.

The default PLL feedback mode is direct compensation mode.

I/O PLLs support the following PLL feedback modes:

Direct compensation
LVDS compensation
Source synchronous compensation
Normal compensation
Zero delay buffer (ZDB) compensation
External feedback (EFB) compensation

Normal and source synchronous compensation modes compensate for the insertion delay of a routed core clock. For Intel^® Agilex™ devices, you can achieve core clock compensation by routing a dedicated feedback clock from the M counter in the I/O PLL to emulate the insertion delay of the compensated C counter output clock network.

Intel recommends the non-dedicated feedback mechanism because it uses the clock resources most efficiently.

2.2.6.1. Direct Compensation Mode

In direct mode, the PLL does not compensate for any clock network delays. This mode provides better jitter performance compared to other compensation modes because the clock feedback into the phase frequency detector (PFD) passes through less circuitry. Both the PLL internal- and external-clock outputs are phase-shifted with respect to the PLL clock input.

Figure 11. Example of Phase Relationship Between the PLL Clocks in Direct Mode

2.2.6.2. LVDS Compensation Mode

LVDS compensation mode maintains the same data and clock timing relationship at the pins of the internal serializer/deserializer (SERDES) capture register, except that the clock is inverted (180° phase shift). Thus, LVDS compensation mode ideally compensates for the delay of the LVDS clock network, including the difference in delay between the following two paths:

Data pin-to-SERDES capture register
Clock input pin-to-SERDES capture register

The output counter must provide the 180° phase shift.

Figure 12. Example of Phase Relationship Between the Clock and Data in LVDS Compensation Mode

2.2.6.3. Source Synchronous Compensation Mode

If the data and clock signals arrive at the same time on the input pins, the same phase relationship is maintained at the clock and data ports of any IOE input register. Data and clock signals at the IOE experience similar buffer delays as long as you use the same I/O standard. Only one output clock can be compensated in source synchronous compensation mode.

Intel recommends source synchronous mode for source synchronous data transfers.

Figure 13. Example of Phase Relationship Between Clock and Data in Source Synchronous Mode

The source synchronous mode compensates for the delay of the clock network used and any difference in the delay between the following two paths:

Data pin to the IOE register input
Clock input pin to the PLL PFD input

The Intel^® Agilex™ PLL can compensate multiple pad-to-input-register paths, such as a data bus when it is set to use source synchronous compensation mode.

2.2.6.4. Normal Compensation Mode

An internal clock in normal compensation mode is phase-aligned to the input clock pin. The external clock output pin has a phase delay relative to the clock input pin if connected in this mode. The Intel^® Quartus^® Prime Timing Analyzer reports any phase difference between the two. In normal compensation mode, the delay introduced by the clock network is fully compensated. Only one output clock can be compensated in normal compensation mode.

Figure 14. Example of Phase Relationship Between the PLL Clocks in Normal Compensation Mode

2.2.6.5. Zero-Delay Buffer Mode

In zero-delay buffer (ZDB) mode, the external clock output pin is phase-aligned with the clock input pin for zero delay through the device. This mode is only supported for I/O bank I/O PLL.

In this mode, you must use the same I/O standard on the input clocks and clock outputs to guarantee clock alignment at the input and output pins. You cannot use differential I/O standards on the PLL clock input or output pins.

To ensure phase alignment between the clk pin and the external clock output (CLKOUT) pin in ZDB mode, instantiate a bidirectional I/O pin in the design. The bidirectional I/O pin serves as the feedback path connecting the fbout and fbin ports of the PLL. The bidirectional I/O pin must always be assigned a single-ended I/O standard, and must not be globally promoted. The PLL uses this bidirectional I/O pin to mimic and compensate for the output delay from the clock output port of the PLL to the external clock output pin.

Note: To avoid signal reflection when using ZDB mode, do not place board traces on the bidirectional I/O pin.

Figure 15. Example of Phase Relationship Between the PLL Clocks in ZDB Mode

2.2.6.6. External Feedback Mode

In external feedback (EFB) mode, the output of the M counter (fbout) feeds back to the PLL fbin input (using a trace on the board) and becomes part of the feedback loop. EFB mode is only supported for I/O bank I/O PLL, not supported for fabric-feeding I/O PLL.

One of the dual-purpose external clock outputs becomes the fbin input pin in this mode. The external feedback input pin, fbin is phase-aligned with the clock input pin. Aligning these clocks allows you to remove clock delay and skew between devices.

In EFB mode, you must use the same I/O standard on the input clock, feedback input, and clock outputs.

Figure 16. Example of Phase Relationship Between the PLL Clocks in EFB Mode

2.2.7. Clock Multiplication and Division

An Intel^® Agilex™ PLL output frequency is related to its input reference clock source by the scale factor: M/(N × C) for I/O PLL.

The input clock is divided by a pre-scale factor, N, and is then multiplied by the M feedback factor. The control loop drives the VCO to match f_in × (M/N). When using non-dedicated feedback path in normal or source synchronous compensation mode, the control loop drives the VCO to match f_in × ((M × C_i)/N), where C_i is the compensated outclk C counter value. The Intel^® Quartus^® Prime software automatically chooses the appropriate scale factors according to the input frequency, multiplication, and division values that you specify in the parameter editor for the IP.

Pre-Scale Counter, `N` and Multiply Counter, `M`

Each PLL has one pre-scale counter, N, and one multiply counter, M. The M and N counters do not use duty-cycle control because the only purpose of these counters is to calculate frequency division.

Post-Scale Counter, `C`

Each output port has a unique post-scale counter, C. For multiple C counter outputs with different frequencies, the VCO is set to the least common multiple of the output frequencies that meets its frequency specifications. For example, if the output frequencies required from one I/O PLL are 55 MHz and 100 MHz, the Intel^® Quartus^® Prime software sets the VCO frequency to 1.1 GHz (the least common multiple of 55 MHz and 100 MHz within the VCO operating frequency range). Then the post-scale counters, C, scale down the VCO frequency for each output port.

Integer Mode

The I/O PLL can only operate in integer mode.

2.2.8. Programmable Phase Shift

The programmable phase shift feature allows only the I/O PLLs to generate output clocks with a fixed phase offset.

The VCO frequency of the PLL determines the precision of the phase shift. The minimum phase shift increment is 1/8 of the VCO period. For example, if an I/O PLL operates with a VCO frequency of 1000 MHz, phase shift steps of 125 ps are possible.

The Intel^® Quartus^® Prime software automatically adjusts the VCO frequency according to the user-specified phase shift values entered into the IP core.

2.2.9. Programmable Duty Cycle

The programmable duty cycle feature allows I/O PLLs to generate clock outputs with a variable duty cycle. This feature is only supported by the I/O PLL post-scale counters, C.

The I/O PLL C counter value determines the precision of the duty cycle. The precision is 50% divided by the post-scale counter value. For example, if the C0 counter is 10, steps of 5% are possible for duty-cycle options from 5% to 90%. If the I/O PLL is in external feedback mode, set the duty cycle for the counter driving the fbin pin to 50%.

The Intel^® Quartus^® Prime software automatically adjusts the VCO frequency according to the required duty cycle that you enter in the IP core.

Combining the programmable duty cycle with programmable phase shift allows the generation of precise non-overlapping clocks.

2.2.10. PLL Cascading

Intel^® Agilex™ devices support PLL-to-PLL cascading. You can cascade a maximum of two PLLs. PLL cascading synthesizes more output clock frequencies than a single PLL.

If you cascade PLLs in your design, the source (upstream) PLL must have a low-bandwidth setting, and the destination (downstream) PLL must have a high-bandwidth setting for I/O PLL. During cascading, the output of the source PLL serves as the reference clock (input) of the destination PLL. The bandwidth settings of cascaded PLLs must be different. If the bandwidth settings of the cascaded PLLs are the same, the cascaded PLLs may amplify phase noise at certain frequencies. Intel^® Agilex™ devices do not support I/O PLL cascading within the same I/O bank.

Intel^® Agilex™ devices support the following PLL-to-PLL cascading modes for I/O bank I/O PLL:

I/O-PLL-to-I/O-PLL cascading via dedicated cascade path—upstream I/O PLL and downstream I/O PLL must be in the same I/O column.
I/O-PLL-to-I/O-PLL cascading via core clock fabric—no restriction on locations of upstream and downstream I/O PLL.

The permit_cal input of the downstream I/O PLL must be connected to the locked output of the upstream I/O PLL in both PLL cascading modes.

The following figures show the connectivity required between the upstream and downstream I/O PLL for both the PLL cascading modes.

Figure 17. I/O-PLL-to-I/O-PLL Cascading Via Dedicated Cascade Path

Figure 18. I/O-PLL-to-I/O-PLL Cascading Via Core Clock Fabric

2.2.11. PLL Input Clock Switchover

The clock switchover feature allows the I/O PLL to switch between two reference input clocks. Use this feature for clock redundancy or for a dual-clock domain application where a system turns to the redundant clock if the previous clock stops running. The design can perform clock switchover automatically when the clock is no longer toggling or based on a user control signal, extswitch.

Intel^® Agilex™ I/O PLLs support the following clock switchover modes:

Automatic switchover—the clock sense circuit monitors the current reference clock. If the current reference clock stops toggling, the reference clock automatically switches to inclk0 or inclk1 clock.
Manual clock switchover—clock switchover is controlled using the extswitch signal. When the extswitch signal goes from logic high to logic low, and stays low for at least three clock cycles for the inclk being switched to, the reference clock to the I/O PLL is switched from inclk0 to inclk1, or vice-versa.
Automatic switchover with manual override—this mode combines automatic switchover and manual clock switchover. When the extswitch signal goes low, it overrides the automatic clock switchover function. As long as the extswitch signal is low, further switchover action is blocked.

2.2.11.1. Automatic Switchover

Intel^® Agilex™ I/O PLLs support a fully configurable clock switchover capability.

Figure 19. Automatic Clock Switchover Circuit Block DiagramThis figure shows a block diagram of the automatic switchover circuit in the I/O PLL.

When the current reference clock is not present, the clock sense block automatically switches to the backup clock for I/O PLL reference. You can select a clock source as the backup clock by connecting it to the inclk1 port of the I/O PLL in your design.

The clock switchover circuit sends out three status signals—clkbad0, clkbad1, and activeclock—from the I/O PLL to implement a custom switchover circuit in the logic array.

In automatic switchover mode, the clkbad0 and clkbad1 signals indicate the status of the two clock inputs. When they are asserted, the clock sense block detects that the corresponding clock input has stopped toggling. These two signals are not valid if the frequency difference between inclk0 and inclk1 is greater than 20%.

The activeclock signal indicates which of the two clock inputs (inclk0 or inclk1) is being selected as the reference clock to the I/O PLL. When the frequency difference between the two clock inputs is more than 20%, the activeclock signal is the only valid status signal.

Use the switchover circuitry to automatically switch between inclk0 and inclk1 when the current reference clock to the I/O PLL stops toggling. You can switch back and forth between inclk0 and inclk1 any number of times when one of the two clocks fails and the other clock is available.

For example, in applications that require a redundant clock with the same frequency as the reference clock, the switchover state machine generates a signal (clksw) that controls the multiplexer select input. In this case, inclk1 becomes the reference clock for the I/O PLL.

When using automatic clock switchover mode, the following requirements must be satisfied:

Both clock inputs must be running when the FPGA is configured.
The period of the two clock inputs can differ by no more than 20%.
The input clocks must meet the input jitter specifications and I/O standard specifications.

Glitches in the input clock may be seen as a greater than 20% difference in frequency between the input clocks.

If the current clock input stops toggling while the other clock is also not toggling, switchover is not initiated and the clkbad[0..1] signals are not valid. If both clock inputs are not the same frequency, but their period difference is within 20%, the clock sense block detects when a clock stops toggling. However, the I/O PLL may lose lock after the switchover is completed and needs time to relock.

Note: You must reset the I/O PLL using the reset signal to maintain the phase relationships between the I/O PLL input and output clocks when using clock switchover.

Figure 20. Automatic Switchover After Loss of Clock DetectionThis figure shows an example waveform of the switchover feature in automatic switchover mode. In this example, the inclk0 signal is held low. After the inclk0 signal is held low for approximately two clock cycles, the clock sense circuitry drives the clkbad0 signal high. As the reference clock signal (inclk0) is not toggling, the switchover state machine controls the multiplexer through the extswitch signal to switch to the backup clock, inclk1.

2.2.11.2. Automatic Switchover with Manual Override

In automatic switchover with manual override mode, you can use the extswitch signal for user- or system-controlled switch conditions. You can use this mode for same-frequency switchover, or to switch between inputs of different frequencies.

For example, if inclk0 is 66 MHz and inclk1 is 200 MHz, you must control switchover using the extswitch signal. The automatic clock-sense circuitry cannot monitor clock input (inclk0 and inclk1) frequencies with a frequency difference of more than 100% (2×).

This feature is useful when the clock sources originate from multiple cards on the backplane, requiring a system-controlled switchover between the frequencies of operation.

You must choose the backup clock frequency and set the M, N, and C counters so that the VCO operates within the recommended operating frequency range. The Intel^® Quartus^® Prime software notifies you if a given combination of inclk0 and inclk1 frequencies cannot meet this requirement.

Figure 21. Clock Switchover Using the extswitch (Manual) ControlThis figure shows a clock switchover waveform controlled by the extswitch signal. In this case, both clock sources are functional and inclk0 is selected as the reference clock. The switchover sequence starts when the extswitch signal goes low. On the falling edge of inclk0, the counter’s reference clock, muxout, is gated off to prevent clock glitching. On the falling edge of inclk1, the reference clock multiplexer switches from inclk0 to inclk1 as the I/O PLL reference. The activeclock signal changes to indicate the clock which is currently feeding the I/O PLL.

In automatic override with manual switchover mode, the activeclock signal inverts after the extswitch signal transitions from logic high to logic low. Since both clocks are still functional during the manual switch, neither clkbad signal goes high. Because the switchover circuit is negative-edge sensitive, the rising edge of the extswitch signal does not cause the circuit to switch back from inclk1 to inclk0. When the extswitch signal goes low again, the process repeats.

The extswitch signal and automatic switch work only if the clock being switched to is available. If the clock is not available, the state machine waits until the clock is available.

2.2.11.3. Manual Clock Switchover

In manual clock switchover mode, the extswitch signal controls whether inclk0 or inclk1 is selected as the input clock to the I/O PLL. By default, inclk0 is selected.

A clock switchover event is initiated when the extswitch signal transitions from logic high to logic low, and is held low for at least three inclk cycles for the inclk clock being switched to.

You must bring the extswitch signal back high again to perform another switchover event. If you do not require another switchover event, you can leave the extswitch signal in a logic low state after the initial switch.

If inclk0 and inclk1 are different frequencies and are always running, the extswitch signal minimum low time must be greater than or equal to three of the slower frequency inclk0 and inclk1 cycles.

Figure 22. Manual Clock Switchover Circuitry in Intel^® Agilex™ I/O PLLs

You can delay the clock switchover action by specifying the switchover delay in the Intel^® FPGA IP cores for the I/O PLL. When you specify the switchover delay, the extswitch signal must be held low for at least three inclk cycles for the inclk being switched to plus the number of the delay cycles that you specify to initiate a clock switchover.

2.2.12. PLL Reconfiguration and Dynamic Phase Shift

There are two I/O bank I/O PLLs inside an I/O bank, one located at the top sub-bank and the other located at the bottom sub-bank. The two I/O bank I/O PLLs share the same IOPLL Reconfig IP ports in the I/O bank. Thus, only the I/O bank I/O PLL located in the top sub-bank can be implemented for PLL reconfiguration and dynamic phase shift. The fabric-feeding I/O PLL has its own IOPLL Reconfig IP ports and can always be reconfigured.

Intel^® Agilex™ devices support PLL reconfiguration and dynamic phase shift with the following features:

PLL reconfiguration—I/O PLL can reconfigure the M, N, C counters, and bandwidth setting.
Dynamic phase shift—I/O PLL can perform positive or negative phase shift. Able to shift multiple phase steps each time, where one phase step is equal to 1/8 of the VCO period.

2.2.13. PLL Calibration

I/O PLLs include both analog and digital blocks that require calibration to compensate for process, voltage, and temperature (PVT) variations. Intel^® Agilex™ uses the I/O manager to perform calibration routines.

There are two main types of calibration.

Power-up calibration—initiates automatically at device power-up and runs during device configuration.
User calibration—if you perform dynamic reconfiguration or change the reference clock frequency of the I/O PLL, you must perform user recalibration. You must enable the required calibration sequence.

To successfully complete the calibration process, OSC_CLK_1 clocks and all reference clocks driving the I/O PLLs must be stable and free running at the start of FPGA configuration. If clock switchover is enabled, both reference clocks must be present for calibration. During user mode, when the I/O PLL does not detect a reference clock during configuration, calibration attempts continue periodically. After calibration has completed, the I/O PLL is locked automatically.

2.2.13.1. Power-Up Calibration

After device power-up, the I/O manager automatically initiates the calibration process. The process continues during device programming.

2.2.13.2. User Calibration

The I/O PLL must be recalibrated for any of the following conditions after device power up:

Dynamic I/O PLL reconfiguration that changes the M or N counter settings is performed.
Change of the reference clock frequency to the I/O PLL.

Recalibration is not necessary when using clock switchover to a secondary reference clock with a different frequency than the primary reference clock. The I/O PLL stores the calibration settings for both reference clocks after power-up calibration.

3. Intel Agilex Clocking and PLL Design Considerations

3.1. Guidelines: Clock Switchover

When implementing clock switchover in Intel^® Agilex™ I/O PLLs, refer to the following guidelines:

Automatic clock switchover requires that the inclk0 and inclk1 frequencies are within 20% of each other. Failing to meet this requirement causes the clkbad0 and clkbad1 signals to not function properly.
When using manual clock switchover, the difference between inclk0 and inclk1 can be more than 100% (2×). However, differences in frequency, phase, or both, of the two clock sources may cause the I/O PLL to lose lock. Resetting the I/O PLL ensures that you maintain the correct phase relationships between the input and output clocks.
Both inclk0 and inclk1 must be running when the extswitch signal goes low to initiate the manual clock switchover event. Failing to meet this requirement causes the clock switchover to not function properly.
Applications that require a clock switchover feature and a small frequency drift must use a low-bandwidth I/O PLL. When referencing input clock changes, the low-bandwidth I/O PLL reacts more slowly than a high-bandwidth I/O PLL. When switchover happens, a low-bandwidth I/O PLL propagates the stopping of the clock to the output more slowly than a high-bandwidth I/O PLL. However, the low-bandwidth I/O PLL also increases lock time.
After a switchover occurs, there may be a finite resynchronization period for the I/O PLL to lock onto a new clock. The time it takes for the I/O PLL to relock depends on the I/O PLL configuration.
If the phase relationship between the input clock to the I/O PLL and the output clock from the I/O PLL is important in your design, assert the reset signal for at least 10 ns after performing a clock switchover. Wait for the locked signal to go high and be stable before re-enabling the output clocks from the I/O PLL.
The VCO frequency gradually decreases when the current clock is lost and then increases as the VCO locks on to the backup clock, as shown in the following figure.

Figure 24. VCO Switchover Operating Frequency

3.2. Guidelines: Timing Closure

For timing closure, refer to the following guidelines:

Reconfiguring a PLL's counter and loop filter settings changes both the output frequency and the clock uncertainty of that I/O PLL. Dynamic phase shift only affects the output clock phase.
The Intel^® Quartus^® Prime Timing Analyzer performs timing analysis for the initial PLL settings only. You must verify that your design closes timing after dynamic reconfiguration or dynamic phase shift.
Intel recommends compiling the I/O PLL designs with each intended configuration setting to determine the variation in the clock with the I/O PLL settings.

3.3. Guidelines: Resetting the PLL

To reset the PLL, refer to the following guidelines:

When changing the M counter, N counter, or loop filter settings, the I/O PLL may lose and regain lock. To maintain the appropriate phase relationship between the reference clock and output clocks, assert the areset signal to reset the I/O PLL after reconfiguration is complete. Intel recommends always resetting the I/O PLL after any reconfiguration operation to the M counter, N counter, or loop filter settings.
When changing the C counter settings, you may lose the expected phase relationship between the C counters. Assert the areset signal after reconfiguration is complete to restore the expected phase relationship. Reset is not required if the phase relationships are not important to your application.
Resetting the I/O PLL does not modify the counter or loop filter settings. However, resetting the I/O PLL undoes any dynamic phase shift operations that were performed. After the I/O PLL is reset, the phase shift on the C counters is restored to the originally programmed settings.

3.4. Guidelines: Configuration Constraints

The I/O PLL configuration must obey the following constraints:

The phase frequency detector (PFD) and VCO each have a legal frequency range of operation.
The loop filter settings must be appropriate for the M counter value and user-selected bandwidth mode.

If any of these configuration constraints are violated, the I/O PLL may fail to lock or may exhibit poor jitter performance.

3.5. Guidelines: I/O PLL Reconfiguration

To reconfigure the I/O PLL, refer to the following guidelines:

If the reference clock frequency changes, you must recalibrate the I/O PLL using the IP core.
The I/O PLL reconfiguration interface must have a free running mgmt_clk signal. The mgmt_clk signal must be less than 100 MHz. This interface eliminates the need to precisely control the start and stop of mgmt_clk signal.
The I/O PLL can be reconfigured with .mif streaming mode and advanced mode using the IP core. Intel recommends using the .mif streaming mode.
Use caution when reconfiguring an I/O PLL with a non-zero phase shift setting. Modifying the M counter or N counter settings does not change the relative phase shift (in percent), but alters the absolute phase shift (in picoseconds). Modifying the C counter settings does not change the absolute phase shift, but modifies the relative phase shift.

3.6. Clocking Constraints

The common clocking constraint commands that are commonly used for clock and PLLs in .sdc file are as follows:

create_clock
create_generated_clock
create_clock_uncertainty

3.7. IP Core Constraints

To implement the IOPLL IP core, you must adhere to the following constraints:

Any SDC design constraints referring to the I/O PLL clocks must be listed after the SDC constraints for the IOPLL IP core.
Intel recommends reading the SDC for all I/O PLLs first in a design. You can do this by listing the IP before others in the .qsf file.

3.8. Guideline: Achieving 5% Duty Cycle for fOUT_EXT ≥ 300 MHz Using tx_outclk Port from LVDS SERDES Intel FPGA IP

To achieve 5% duty cycle for f_{OUT_EXT} ≥ 300 MHz, you can only use tx_outclk port from the LVDS SERDES Intel^® FPGA IP. Refer to the following guidelines for the settings in the LVDS SERDES Intel^® FPGA IP:

In the General Setting tab, select TX as functional mode. For data rate, enter a value 2× of your desired frequency. As an example, if your desired frequency is 500 MHz, enter 1000 as data rate.
In the PLL settings tab, set your desired input frequency.
In the Transmitter Settings tab, enable tx_outclock port and select 2 as Tx_outclock division factor.

4. Clock Control Intel FPGA IP Core

The Clock Control IP core provides clock control features such as enabling entry to the clock network, clock multiplexing, clock gating, and clock division for the Intel^® Agilex™ devices.

4.1. Release Information for Clock Control Intel FPGA IP

Intel^® FPGA IP versions match the Intel^® Quartus^® Prime Design Suite software versions until v19.1. Starting in Intel^® Quartus^® Prime Design Suite software version 19.2, Intel^® FPGA IP has a new versioning scheme.

The Intel^® FPGA IP version (X.Y.Z) number can change with each Intel^® Quartus^® Prime software version. A change in:

X indicates a major revision of the IP. If you update the Intel^® Quartus^® Prime software, you must regenerate the IP.
Y indicates the IP includes new features. Regenerate your IP to include these new features.
Z indicates the IP includes minor changes. Regenerate your IP to include these changes.

Table 4. Clock Control Intel^® FPGA IP Core Current Release Information
Item	Description
IP Version	2.0.0
Intel^® Quartus^® Prime Version	20.3
Release Date	2020.09.28

4.2. Clock Control IP Core Parameters

Table 5. Clock Control IP Core Parameters for Intel^® Agilex™ Devices
Parameter	Value	Description
Number of Clock Inputs	1, 2, or 4	Specify the number of input clock sources for the clock control block. You can specify up to four clock inputs. Clock multiplexing in Intel^® Agilex™ devices is implemented using soft logic in the core.
Ensure glitch free clock switchover	On or Off	Turn on this option to implement a glitch-free switchover when you use multiple clock inputs. You must ensure the currently selected clock is running before switching to another source. If the selected clock is not running, you cannot switch to the new clock source using the glitch-free switchover implementation. By default, the `clkselect` port is set to `00`. You must apply a clock to `inclk0x` to read the values on the `clkselect` ports. This feature will be available in a future release.
Clock Enable	On or Off	Turn on this option if you want to gate your clock output with an enable signal. This option disables the option to use clock division.
Clock Enable Type	Root Level or Distributed Sector Level	Select the clock gates located in the periphery or the gates located in the sector. For more information about the clock gates, refer to the Clock Gating section.
Enable Register Mode	Negative Latch or None	Specify if the enable signal should be latched.
Clock Divider	On or Off	Turn on this option if you want to use the clock division block in the periphery.
Clock Divider Output Ports	Divide 1x, Divide 1x and 2x, or Divide 1x, 2x and 4x	Specify the combination of passing your clock through, dividing your clock by 2, or dividing your clock by 4.

4.3. Clock Control IP Core Ports and Signals

Table 6. Clock Control IP Core Ports for Intel^® Agilex™ Devices
Port Name	Description
`inclk`	Input signal to the clock network.
`inclk0x`, `inclk1x`, `inclk2x`, `inclk3x`	Input signals to the clock network based on the value selected for the Number of Clock Inputs parameter.
`clkselect[]`	Input that dynamically selects the clock source to drive the clock network that is driven by the clock buffer. Input port `[1 DOWNTO 0]` wide. The following list shows the signal selection for the `clkselect[]` value: `2’b00` selects `inclk0x` `2’b01` selects `inclk1x` `2’b10` selects `inclk2x` `2’b11` selects `inclk3x`
`outclk`	Output of the Clock Control IP core when Clock Divider option is not selected.
`ena`	Clock enable of the clock gate block. This signal is active-high.
`clock_div1x`, `clock_div2x`, `clock_div4x`	Outputs of the Clock Control IP core when the Clock Divider option is selected. The exact combination of ports exposed depends on the value specified for the Clock Divider Output Ports parameter. `clock_div1x` is the same as `inclk` `clock_div2x` divides `inclk` by 2 `clock_div4x` divides `inclk` by 4

5. IOPLL Intel FPGA IP Core

The IOPLL IP core allows you to configure the settings of the Intel^® Agilex™ I/O PLL.

The IOPLL IP core supports the following features:

Supports six different clock feedback modes: direct, external feedback, normal, source synchronous, zero delay buffer, and LVDS mode.
Generates up to seven output clocks for I/O bank I/O PLL and three output clocks for fabric-feeding I/O PLL for the Intel^® Agilex™ device.
Switches between two reference input clocks.
Supports adjacent PLL (adjpllin) input to connect with an upstream PLL in PLL dedicated cascading mode.
Generates the Memory Initialization File (.mif) and allows PLL dynamic reconfiguration.
Supports PLL dynamic phase shift.

5.1. Release Information for IOPLL Intel FPGA IP

The Intel^® FPGA IP version (X.Y.Z) number can change with each Intel^® Quartus^® Prime software version. A change in:

X indicates a major revision of the IP. If you update the Intel^® Quartus^® Prime software, you must regenerate the IP.
Y indicates the IP includes new features. Regenerate your IP to include these new features.
Z indicates the IP includes minor changes. Regenerate your IP to include these changes.

Table 7. IOPLL Intel^® FPGA IP Core Current Release Information
Item	Description
IP Version	19.3.1
Intel^® Quartus^® Prime Version	20.3
Release Date	2020.09.28

5.2. .mif File Generation

You can generate the .mif files in the IOPLL IP core parameter editor. You must use the .mif file with the IOPLL Reconfig Intel^® FPGA IP core.

5.2.1. Generating a New .mif File

To generate a new .mif file containing a single I/O PLL configuration, follow these steps:

At the Dynamic Reconfiguration tab, select Enable dynamic reconfiguration of PLL.
For MIF Generation Options, select Generate New MIF File.
For Path of New MIF file, specify a file name.
For Name of Current Configuration, specify the name of the current configuration of the I/O PLL.
Click Create MIF File.

5.2.2. Adding Configurations to Existing .mif File

You can append new configurations to an existing .mif file. To store more configurations in a .mif file, follow these steps:

At the Dynamic Reconfiguration tab, select Enable dynamic reconfiguration of PLL.
For MIF Generation Options, select Add Configuration to Existing MIF File.
For Path of New MIF file, specify a file name.
For Name of Current Configuration, specify the name of the new configuration of the I/O PLL.
Click Append to MIF File.

5.3. IP-XACT File Generation

You can generate the IP-XACT files in the IOPLL IP core parameter editor. You can use the IP-XACT files to determine addresses of reconfigurable bits in the IOPLL IP core.

5.3.1. Generating a New IP-XACT File

To generate a new IP-XACT file, follow these steps:

On the IOPLL Intel FPGA IP dialog box, click Generate HDL.
Ensure either Verilog or VHDL is selected for the Create HDL design files for synthesis option. Click Generate to generate the IP-XACT file.

The following IP-XACT files are generated:

agilex_iobank_pll.ipxact file—When IOPLL Type is I/O Bank
agilex_fabric_pll.ipxact file—When IOPLL Type is Fabric-Feeding

5.4. IOPLL IP Core Parameters

The IOPLL IP core is available under the PLL category of the IP Catalog.

5.4.1. IOPLL IP Core Parameters - PLL Tab

Table 8. IOPLL IP Core Parameters - PLL Tab for Intel^® Agilex™ Devices
Parameter	Value	Description
Device Family	Intel^® Agilex™	Specifies the device family.
Component	—	Specifies the targeted device.
Speed Grade	—	Specifies the speed grade for targeted device.
IOPLL Type	Fabric-Feeding, I/O Bank	Select the type of the I/O PLL. The fabric-feeding I/O PLL locations have fewer `outclks` than the I/O bank I/O PLLs, and cannot be used as External I/O PLL in the LVDS SERDES Intel^® FPGA IP core.
Reference Clock Frequency	—	Specifies the input frequency for the input clock, `refclk`, in MHz. The default value is 100.0 MHz. The minimum and maximum value is dependent on the selected device.
Refclk source is global clock	On or Off	Specifies whether the reference clock source is a global clock. Intel recommends using a dedicated reference clock pin instead of a global clock to minimize jitter. If a global reference clock source is required, this clock must still be promoted using the Assignment Editor.
Enable Locked Output Port	On or Off	Turn on to enable the `locked` port.
Enable physical output clock parameters	On or Off	Turn on to enter physical PLL counter parameters instead of specifying a desired output clock frequency.
Compensation Mode	direct, external feedback ⁶, normal, source synchronous, zero delay buffer ⁶, or lvds ⁶	Specifies the operation of the PLL. The default operation is direct mode. If you select the direct mode, the PLL minimizes the length of the feedback path to produce the smallest possible jitter at the PLL output. The internal-clock and external-clock outputs of the PLL are phase-shifted with respect to the PLL clock input. In this mode, the PLL does not compensate for any clock networks. If you select the external feedback mode, you must connect the `fbclk` input port to an input pin. A board-level connection must connect both the input pin and external clock output port, `fboutclk`. The `fbclk` port is aligned with the input clock. If you select the normal mode, the PLL compensates for the delay of the internal clock network used by the clock output. If the PLL is also used to drive an external clock output pin, a corresponding phase shift of the signal on the output pin occurs. If you select the source synchronous mode, the clock delay from pin to I/O input register matches the data delay from pin to I/O input register. If you select the zero delay buffer mode, the PLL must feed an external clock output pin and compensate for the delay introduced by that pin. The signal observed on the pin is synchronized to the input clock. The PLL clock output connects to the `altbidir` port and drives `zdbfbclk` as an output port. If the PLL also drives the internal clock network, a corresponding phase shift of that network occurs. If you select the lvds mode, the same data and clock timing relationship of the pins at the internal SERDES capture register is maintained. The mode compensates for the delays in LVDS clock network, and between the data pin and clock input pin to the SERDES capture register paths.
Compensated Outclk ⁷	0–6	Allows you to select which output clock (`outclk`) to be compensated. The feedback mode compensates for the clock network delay of the `outclk` selected. This feedback mode ensures correct phase relationship between I/O PLL input and output clocks only for the selected `outclk`.
Use Nondedicated Feedback Path ⁷	On or Off	Turn on to conserve clock resources and improve timing analysis. However, this feature creates frequency limitations and disables phase shift.
Number of Clocks	1–3 (fabric-feeding), 1–7 (I/O bank)	Specifies the number of output clocks required for each device in the PLL design. The requested settings for output frequency, phase shift, and duty cycle are shown based on the number of clocks selected.
Multiply Factor (M-Counter) ⁸	4–160	Specifies the multiply factor of `M`-counter.
Divide Factor (N-Counter) ⁸	1–110	Specifies the divide factor of `N`-counter.
Specify VCO Frequency	On or Off	Allows you to restrict the VCO frequency to the specified value. This is useful when creating a PLL for LVDS external mode, or if a specific dynamic phase shift step size is desired.
Desired VCO Frequency ⁹	—	Specifies the VCO frequency for the PLL in MHz. The default value is 600.0 MHz.
Actual VCO Frequency	—	When Enable physical output clock parameters is turned on—displays the VCO frequency based on the values for Reference Clock Frequency, Multiply Factor (M-Counter), and Divide Factor (N-Counter). When Enable physical output clock parameters is turned off and Specify VCO frequency is turned on—allows you to specify the requested value for the VCO frequency. The default value is 600.0 MHz.
Give clock global name	On or Off	Allows you to rename the output clock name.
Clock Name	—	The user clock name for Synopsis Design Constraints (SDC).
Divide Factor (C-Counter) ⁸	1–512	Specifies the divide factor for the output clock (`C`-counter).
Desired Frequency	—	Specifies the output clock frequency of the corresponding output clock port, `outclk[]`, in MHz. The default value is 100.0 MHz. The minimum and maximum values depend on the device used. The PLL only reads the numerals in the first six decimal places.
Actual Frequency	—	Allows you to select the actual output clock frequency from a list of achievable frequencies. The default value is the closest achievable frequency to the desired frequency.
Phase Shift units	ps or degrees	Specifies the phase shift unit for the corresponding output clock port, `outclk[]`, in picoseconds (ps) or degrees.
Desired Phase Shift	—	Specifies the requested value for the phase shift. The default value is 0 ps.
Actual Phase Shift	—	Allows you to select the actual phase shift from a list of achievable phase shift values. The default value is the closest achievable phase shift to the desired phase shift.
Desired Duty Cycle	0.0–100.0	Specifies the requested value for the duty cycle. The default value is 50.0%.
Actual Duty Cycle	—	Allows you to select the actual duty cycle from a list of achievable duty cycle values. The default value is the closest achievable duty cycle to the desired duty cycle.

⁶ This option is only available when selecting I/O Bank on the IOPLL Type.

⁷ This option is only available when either normal or source synchronous mode is selected.

⁸ This parameter is only available when Enable physical output clock parameters is turned on.

⁹ This parameter is only available when Specify VCO Frequency is turned on and Enable physical output clock parameters is turned off.

5.4.2. IOPLL IP Core Parameters - Settings Tab

Table 9. IOPLL IP Core Parameters - Settings Tab for Intel^® Agilex™ Devices
Parameter	Value	Description
PLL Bandwidth Preset	Low ¹⁰, Medium, or High	Specifies the PLL bandwidth preset setting. The default selection is Medium for fabric-feeding I/O PLL, and Low for I/O bank I/O PLL.
Lock Threshold Setting	Low Lock Time, Medium Lock Time, or High Lock Time	This setting determines the sensitivity of the I/O PLL when detecting lock. This is a tradeoff between the time it takes to lock and the accuracy of the `outclk` frequency when `locked` is first asserted. For applications that require the I/O PLL to lock quickly, Low Lock Time is the best option. The estimated lock times are 30 µs + `a` × `refclk_period`, where `a` is 100, 2048, and 4095 for Low Lock Time, Medium Lock Time, and High Lock Time respectively.
PLL Auto Reset	On or Off	Automatically self-resets the PLL on loss of lock.
Create a second input clk ‘refclk1’	On or Off	Turn on to provide a backup clock attached to your PLL that can switch with your original reference clock.
Second Reference Clock Frequency ¹¹	—	Selects the frequency of the second input clock signal. The default value is 100.0 MHz. The minimum and maximum value is dependent on the device used.
Create an ‘active_clk’ signal to indicate the input clock in use ¹¹	On or Off	Turn on to create the `activeclk` output. The `activeclk` output indicates the input clock which is in use by the PLL. Output signal low indicates `refclk` and output signal high indicates `refclk1`.
Create a ‘clkbad’ signal for each of the input clocks ¹¹	On or Off	Turn on to create two `clkbad` outputs, one for each input clock. Output signal low indicates the clock is working and output signal high indicates the clock is not working.
Switchover Mode ¹¹	Automatic Switchover, Manual Switchover, or Automatic Switchover with Manual Override	Specifies the switchover mode for design application. The IP supports three switchover modes: If you select the Automatic Switchover mode, the PLL circuitry monitors the selected reference clock. If one clock stops, the circuit automatically switches to the backup clock in a few clock cycles and updates the status signals, `clkbad` and `activeclk`. If you select the Manual Switchover mode, when the control signal, `extswitch`, changes from logic high to logic low, and stays low for at least three clock cycles, the input clock switches to the other clock. The `extswitch` can be generated from FPGA core logic or input pin. If you select Automatic Switchover with Manual Override mode, when the `extswitch` signal is high, it overrides the automatic switch function. As long as `extswitch` remains high, further switchover action is blocked. To select this mode, your two clock sources must be running and the frequency of the two clocks cannot differ by more than 20%. If both clocks are not on the same frequency, but their period difference is within 20%, the clock loss detection block detects the lost clock. The PLL most likely drops out of lock after the PLL clock input switchover and needs time to lock again.
Switchover Delay ¹¹	0–7	Adds a specific amount of cycle delay to the switchover process.
Access to PLL LVDS_CLK/LOADEN output port ¹⁰	Disabled, Enable LVDS_CLK/LOADEN 0, or Enable LVDS_CLK/LOADEN 0 & 1	Select Enable LVDS_CLK/LOADEN 0 or Enable LVDS_CLK/LOADEN o & 1 to enable the PLL `lvds_clk` or `loaden` output port. Enables this parameter in case the PLL feeds an LVDS SERDES block with external PLL. When using the I/O PLL `outclk` ports with LVDS ports, `outclk[0..3]` are used for `lvds_clk[0,1]` and `loaden[0,1]` ports, `outclk4` can be used for `coreclk` ports.
Enable access to the PLL DPA output port ¹⁰	On or Off	Turn on to enable the PLL DPA output port.
Enable access to PLL external clock output port	On or Off	Turn on to enable the PLL external clock output port.
Specifies which outclk to be used as extclk_out[0] source	C0–C6 (I/O bank)	Specifies the `outclk` port to be used as `extclk_out[0]` source.
Specifies which outclk to be used as extclk_out[1] source	C0–C6 (I/O bank)	Specifies the `outclk` port to be used as `extclk_out[1]` source.

¹⁰ This option is only available when selecting I/O Bank on the IOPLL Type.

¹¹ This parameter is only available when Create a second input clk 'refclk1' is turned on.

5.4.3. IOPLL IP Core Parameters - Cascading Tab

Table 10. IOPLL IP Core Parameters - Cascading Tab
Parameter	Value	Description
Connect to an upstream PLL through Core clock Network Cascading (create a permit_cal input signal)	On or Off	Turn on to create an input port to enable destination (downstream) PLL power-up calibration. Connect source (upstream) PLL `locked` signal to this input port.
Create a ‘cascade out’ signal to connect with a downstream PLL ¹²	On or Off	Turn on to create the `cascade_out` port, which indicates that this PLL is a source and connects with a destination (downstream) PLL.
cascade_out source ¹²	0–6	Specifies which output clock to be used as cascading source.
Create an adjpllin or cclk signal to connect with an upstream PLL ¹²	On or Off	Turn on to create an input port, which indicates that this PLL is a destination and connects with a source (upstream) PLL.

¹² This option is only available when selecting I/O Bank on the IOPLL Type.

5.4.4. IOPLL IP Core Parameters - Dynamic Reconfiguration Tab

Table 11. IOPLL IP Core Parameters - Dynamic Reconfiguration Tab for Intel^® Agilex™ Devices
Parameter	Value	Description
Enable dynamic reconfiguration of PLL	On or Off	Turn on to enable the dynamic reconfiguration of this PLL (in conjunction with the IOPLL Reconfig Intel^® FPGA IP core).
Enable access to dynamic phase shift ports	On or Off	Turn on to enable the dynamic phase shift interface with the PLL.
MIF Generation Option ¹³	Generate New MIF File, Add Configuration to Existing MIF File, or Create MIF File during IP Generation	Either create a new .mif file containing the current configuration of the I/O PLL by clicking Create MIF File or add this configuration to an existing .mif file by clicking Append to MIF File. A .mif file also can be opted to be generated during IP generation. The generated .mif file contains current PLL profile and a collection of physical parameters—such as `M`, `N`, `C`, `K`, bandwidth, and charge pump—that defines that PLL. You can use this .mif file during dynamic reconfiguration to reconfigure the I/O PLL to its current settings.
Path to New/Existing MIF file ¹³	—	Enter location and file name of the new .mif file to be created or existing .mif file to be appended.
Name of Current Configuration ¹³	—	Enter the file name of the existing .mif file you intend to add to.

¹³ This parameter is only available when Enable dynamic reconfiguration of PLL is turned on.

5.4.5. IOPLL IP Core Parameters - Advanced Parameters Tab

Table 12. IOPLL IP Core Parameters - Advanced Parameters Tab for Intel^® Agilex™ Devices
Parameter	Value	Description
Advanced Parameters	—	Displays a table of physical PLL settings that are implemented based on your input.

I/O bank I/O PLL supports a maximum of 7 output clocks. The IOPLL IP core implements the output clocks using C1 to C7 counters.

Fabric-feeding I/O PLL supports a maximum of 3 output clocks. The IOPLL IP core implements the output clocks using C1 to C3 counters.

Table 13. Output Clocks and C Counters Mapping
Output Clock	C Counter
`outclk0`	`C1`
`outclk1`	`C2`
`outclk2`	`C3`
`outclk3`	`C4`
`outclk4`	`C5`
`outclk5`	`C6`
`outclk6`	`C7`

5.5. IOPLL IP Core Ports and Signals

Table 14. IOPLL IP Core Ports for Intel^® Agilex™ Devices
Port Name	Type	Condition	Description
`refclk`	Input	Required	The reference clock source that drives the I/O PLL.
`rst`	Input	Required	The asynchronous reset port for the output clocks. Drive this port high to reset all output clocks to the value of 0.
`fbclk`	Input	Optional	The external feedback input port for the I/O PLL. The IOPLL IP core creates this port when the I/O PLL is operating in external feedback mode or zero-delay buffer mode. To complete the feedback loop, a board-level connection must connect the `fbclk` port and the external clock output port of the I/O PLL.
`fboutclk`	Output	Optional	The port that feeds the `fbclk` port through the mimic circuitry. The `fboutclk` port is available only if the I/O PLL is in external feedback mode.
`zdbfbclk`	Bidirectional	Optional	The bidirectional port that connects to the mimic circuitry. This port must connect to a bidirectional pin that is placed on the positive feedback dedicated output pin of the I/O PLL. The `zdbfbclk` port is available only if the I/O PLL is in zero-delay buffer mode.
`locked`	Output	Optional	The IOPLL IP core drives this port high when the PLL acquires lock. The port remains high as long as the I/O PLL is locked. The I/O PLL asserts the `locked` port when the phases and frequencies of the reference clock and feedback clock are the same or within the lock circuit tolerance. When the difference between the two clock signals exceeds the lock circuit tolerance, the I/O PLL loses lock.
`refclk1`	Input	Optional	Second reference clock source that drives the I/O PLL for clock switchover feature.
`extswitch`	Input	Optional	Active low signal. Assert the `extswitch` signal low (1’b0) for at least three clock cycles to manually switch the clock.
`activeclk`	Output	Optional	Output signal to indicate which reference clock source is in used by I/O PLL.
`clkbad`	Output	Optional	Output signal that indicates the status of reference clock source is good or bad.
`cascade_out`	Output	Optional	Output signal that feeds into downstream I/O PLL.
`adjpllin`	Input	Optional	Input signal that feeds from upstream I/O PLL.
`outclk_[]`	Output	Optional	Output clock from I/O PLL.
`permit_cal`	Input	Optional	This is an input port for the downstream I/O PLL. Connect this `permit_cal` port to the `locked` output port of the upstream I/O PLL. Connecting this `permit_cal` port ensures that the cascaded I/O PLLs are calibrated in the correct order.

6. IOPLL Reconfig Intel FPGA IP Core

You can use Intel^® Agilex™ devices to implement phase-locked loop (PLL) reconfiguration and dynamic phase shift for I/O PLLs.

The Intel^® Agilex™ I/O PLL supports dynamic reconfiguration when the device is in user mode. With the dynamic reconfiguration feature, you can reconfigure the I/O PLL settings in real time. You can change the divide settings of the PLL counters and the PLL bandwidth settings (loop filter setting and charge pump setting) through an Avalon^® memory-mapped interface in the IOPLL Reconfig IP core, without the need to reconfigure the entire FPGA. The Intel^® Agilex™ I/O PLL uses divide counters (N, M, and C counters) and a voltage-controlled oscillator (VCO) to synthesize the desired phase and frequency output.

You can use the IOPLL Reconfig IP core as follows:

Memory Initialization File (.mif) streaming reconfiguration
- Allows the I/O PLL reconfiguration using predefined settings saved in an on-chip ROM. You can store many unique PLL configurations in a single ROM.
- The .mif file is generated automatically by the IOPLL IP core. Using the generated .mif file during .mif streaming reconfiguration ensures the legality of the new configuration.
- Intel recommends using this reconfiguration method.
Advanced mode reconfiguration
- This method of reconfiguration is for advanced users. You must ensure the reconfigured PLL settings are within the legal range.
- Enable the Advanced Reconfiguration option from the IOPLL Reconfig IP core to reconfigure the individual I/O PLL registers.
- This method is error prone and may lead to the I/O PLL being reconfigured into an illegal configuration if the reconfiguration is done incorrectly.
Recalibration of the I/O PLL using .mif
- Perform recalibration of the I/O PLL without any reconfiguration.
- Trigger recalibration if the reference clock frequency changes.
I/O PLL clock gating
- Gate and un-gate I/O PLL output clock 0 to output clock 7 of the I/O PLL.

You can perform dynamic phase shift using the IOPLL Reconfig IP core.

6.1. Release Information for IOPLL Reconfig Intel FPGA IP

The Intel^® FPGA IP version (X.Y.Z) number can change with each Intel^® Quartus^® Prime software version. A change in:

X indicates a major revision of the IP. If you update the Intel^® Quartus^® Prime software, you must regenerate the IP.
Y indicates the IP includes new features. Regenerate your IP to include these new features.
Z indicates the IP includes minor changes. Regenerate your IP to include these changes.

Table 15. IOPLL Reconfig Intel^® FPGA IP Core Current Release Information
Item	Description
IP Version	19.4.0
Intel^® Quartus^® Prime Version	20.2
Release Date	2020.06.22

6.2. Implementing I/O PLL Reconfiguration in the IOPLL Reconfig IP Core

You can enable the PLL reconfiguration circuitry for the I/O PLL through the Avalon^® memory-mapped interface in the IOPLL Reconfig IP core.

6.2.1. Connectivity between the IOPLL and IOPLL Reconfig IP Cores

Figure 25. Connectivity between the IOPLL and IOPLL Reconfig IP Cores in the Intel^® Quartus^® Prime Software

6.2.2. Connecting the IOPLL and IOPLL Reconfig IP Cores

To connect the IOPLL and IOPLL Reconfig IP cores in your design, follow these steps:

Connect the reconfig_to_pll[29..0] bus on the IOPLL Reconfig IP core to the reconfig_to_pll[29..0] bus on the IOPLL IP core.
Connect the reconfig_from_pll[10..0] bus on the IOPLL Reconfig IP core to the reconfig_from_pll[10..0] bus on the IOPLL IP core.
Connect the mgmt_clk port to a valid clock source.
Connect the mgmt_reset port, mgmt_waitrequest port, mgmt_read port, mgmt_write port, mgmt_readdata[7..0] bus, mgmt_writedata[7..0] bus, and mgmt_address[9..0] bus to user control logic to perform read and write operations.

6.3. IOPLL Reconfig IP Core Reconfiguration Modes

The IOPLL Reconfig IP core has four functional reconfiguration modes. The reconfiguration operation mode is based on the setting in the mgmt_address[9:8] bit.

Table 16. IOPLL Reconfig IP Core Reconfiguration Modes
Reconfiguration Mode	`mgmt_address[9:8]`
.mif streaming reconfiguration	2'b 00
Advanced mode reconfiguration	2'b 01
Clock gating reconfiguration	2'b 10
Dynamic phase shift reconfiguration	2'b 11

After performing dynamic reconfiguration on the I/O PLL that changes the M counter, N counter, bandwidth setting, or charge pump current, the I/O PLL must be recalibrated. For .mif streaming reconfiguration, the recalibration is done automatically. For advanced mode reconfiguration, you must manually trigger the recalibration of the I/O PLL. Recalibration is not needed for clock gating and dynamic phase shift reconfiguration.

6.3.1. .mif Streaming Reconfiguration

.mif streaming allows you to dynamically reconfigure the I/O PLL through the IOPLL Reconfig IP core using predefined settings saved in an on-chip RAM. You must generate a .mif file containing these pre-defined configurations, up to 32 I/O PLL configurations, from the IOPLL IP core parameter editor.

To perform .mif streaming reconfiguration, follow these steps:

Set mgmt_address[9:8] = 2’b00 to choose the .mif streaming mode and set mgmt_writedata[4:0] to the index of the desired configuration in the .mif file.
To start the .mif streaming reconfiguration on the I/O PLL, assert the mgmt_write signal for one mgmt_clk cycle. mgmt_waitrequest is asserted by the IOPLL Reconfig IP core while .mif streaming is in progress.
After the reconfiguration is complete, the mgmt_waitrequest signal is de-asserted.
In the IOPLL Reconfig IP core parameter editor, select the Assert waitrequest until IOPLL has locked option for the I/O PLL to lock. Otherwise, you can wait for the I/O PLL to lock to ensure the I/O PLL reconfiguration is complete.

Recalibration is done automatically for .mif streaming reconfiguration. If you want to manually trigger recalibration using .mif file, follow the steps in the Recalibration Using .mif section.

6.3.1.1. Recalibration Using .mif

Recalibration using .mif only allows you to recalibrate the I/O PLL but not to reconfigure the I/O PLL. In the IOPLL Reconfig IP core, enable Recalibration Mode. When the recalibration is selected, a recalibration.mif file is generated automatically for the recalibration operation.

To perform I/O PLL recalibration using .mif, follow these steps:

Set mgmt_address[9:8] = 2’b00 to choose the .mif mode and set mgmt_writedata[4:0] = 2'b00.
To start the recalibration using .mif on the I/O PLL, assert the mgmt_write signal for one mgmt_clk cycle. mgmt_waitrequest is asserted by the IOPLL Reconfig IP core while recalibration is in progress.
After the recalibration is complete, the mgmt_waitrequest signal is deasserted.

6.3.2. Advanced Mode Reconfiguration

In advanced mode, individual I/O PLL setting is reconfigured using the IOPLL Reconfig IP core through the Avalon^® interface.

Advanced mode reconfiguration is only recommended for advanced users. This reconfiguration mode has several limitations and can cause the I/O PLL to lose lock and can lead to device reliability problems if you set the configuration parameters to the illegal configuration settings. Intel recommends using the .mif streaming reconfiguration.

The limitations of using the advanced mode reconfiguration are as follows:

You must ensure that the configuration setting is a legal value so that the I/O PLL has a legal configuration. To ensure your configuration is legal, refer to the IOPLL IP Core Parameters - Advanced Parameters Tab table for the correct configuration settings.
If the value to be reconfigured makes up only a part of one byte in the I/O PLL’s internal memory, you must perform a read-modify-write operation to not overwrite the remaining bits of the byte.
You must manually trigger recalibration of the I/O PLL after the advanced mode reconfiguration.

CAUTION:

PLL may lose lock and can cause reliability problems to your device if you configure with the wrong PLL setting, configure the wrong bit, or overwrite the whole byte for settings that made up just part of one byte.

To perform I/O PLL reconfiguration using advanced mode, follow these steps:

Enable the Advanced Reconfiguration option in the IOPLL Reconfig IP core.
Set mgmt_address[9:8] = 2’b01 to choose the advanced mode reconfiguration.
Set the address bus value for mgmt_address[7:0] and the data bus value for mgmt_writedata [7:0] as the desired PLL setting.
For more details, refer to the Address Bus and Data Bus Settings for Advanced Mode Reconfiguration table.
Assert the mgmt_write signal for one mgmt_clk cycle.
Repeat step 1 until step 3 to set address bus and data bus value for the desired I/O PLL reconfiguration setting.
After the I/O PLL reconfiguration is complete, you must manually trigger the I/O PLL recalibration.
For more details about the I/O PLL recalibration, refer to the Recalibration Using Advanced Mode section.

6.3.2.1. Recalibration Using Advanced Mode

To perform I/O PLL recalibration using advanced mode, follow these steps:

Set mgmt_address[9:8] = 2’b01 to choose the advanced mode.
Set the mgmt_writedata[6] to 1’b1 on mgmt_address[7:0] = 8’b01001001 by performing the read-modify-write operation.
Set mgmt_address[7:0] = 8’b01001010 and mgmt_wriredata[7:0] = 8’b00000011 to enable the calibration interface.

6.3.3. Clock Gating Reconfiguration

You can gate (disable) and un-gate (enable) I/O PLL output clock 0 to output clock 7 of the I/O PLL. It is easily done by writing one byte to the IOPLL Reconfig IP core, with one bit corresponding to each of the I/O PLL output clocks.

To perform clock gating reconfiguration, follow these steps:

Set mgmt_address[9:8] to 2’b10 to select clock gating mode and set mgmt_writedata[7:0] to indicate desired output clock to be gated.
To start the clock gating reconfiguration on the I/O PLL, assert the mgmt_write signal for one mgmt_clk cycle.
The gating changes may not come into effect for multiple clock cycles after mgmt_waitrequest has been de-asserted.

6.3.4. Dynamic Phase Shift Reconfiguration

The dynamic phase shifts reconfiguration can determine the number of shifts, the direction of the phase shift and the output clock to be shifted.

To perform dynamic phase shift reconfiguration through the IOPLL Reconfig IP core, follow these steps:

Set mgmt_address[9:8] to 2’b11 to select dynamic phase shift reconfiguration mode.
set mgmt_writedata[7:0] to indicate the desired number of phase shift, the direction of phase shift, and the desired counter to be shifted.
To start the dynamic phase shift reconfiguration on the I/O PLL, assert the mgmt_write signal for one mgmt_clk cycle. This signal is the equivalent of the phase_en signal on the I/O PLL.
After the dynamic phase shift is complete, the mgmt_waitrequest signal is de-asserted.

6.4. Avalon Memory-Mapped Interface Ports in the IOPLL Reconfig IP Core

Table 17. Avalon^® Memory-Mapped Interface Ports in the IOPLL Reconfig IP Core for Intel^® Agilex™ Devices
Port	Direction	Description
`mgmt_clk`	Input	Dynamic reconfiguration clock that drives the IOPLL Reconfig IP core. The maximum input clock frequency is 100 MHz. This clock can be an independent clock source. It must be free running, which means it cannot be connected to the output of the I/O PLL being reconfigured.
`mgmt_reset`	Input	Active high signal. Synchronous reset input to clear all the data in the IOPLL Reconfig IP core.
`mgmt_waitrequest`	Output	This port goes high when PLL reconfiguration process started and remains high during PLL reconfiguration. After PLL reconfiguration process completed, this port goes low.
`mgmt_write`	Input	Active high signal. Asserts to indicate a write operation.
`mgmt_read`	Input	Active high signal. Asserts to indicate a read operation.
`mgmt_writedata[7..0]`	Input	Writes data to this port when `mgmt_write` signal is asserted.
`mgmt_readdata[7..0]`	Output	Reads data from this port when `mgmt_read` signal is asserted.
`mgmt_address[9..0]`	Input	Specifies the address of the data bus for a read or write operation.
`reconfig_from_pll[10..0]`	Input	Bus that connects to `reconfig_from_pll[10..0]` bus in the IOPLL Intel^® FPGA IP core.
`reconfig_to_pll[29..0]`	Output	Bus that connects to `reconfig_to_pll[29..0]` bus in the IOPLL IP core.

6.5. Address Bus and Data Bus Settings

Assign a value of “0” for all the unused bits in the address bus and the data bus during reconfiguration operations.

6.5.1. Address Bus and Data Bus Settings for Advanced Mode Reconfiguration

Table 18. Address Bus and Data Bus Settings for Advanced Mode Reconfiguration
Register Name		Address (Binary)	Counter Bit Setting
`M` Counter	High Count	00000100	`Data[7:0]` = `high_count` `Data[7:0]` = `low_count` `total_count` = `high_count` + `low_count`
	Low Count	00000111
	Bypass Enable ¹⁴	00000101	`Data[0]` = bypass enable `Data[0]` = 1, bypass is enabled. The counter is bypassed with counter division value = 1.
	Odd Division ¹⁴	00000110	`Data[7]` = Odd division `Data[7]` = 0, odd division is disabled. The selected counter duty cycle = `high_count`/`total_count`. `Data[7]` = 1, odd division enabled. The selected counter duty cycle = (`high_count` – 0.5)/`total_count`.
`N` Counter	High Count	00000000	`Data[7:0]` = `high_count` `Data[7:0]` = `low_count` `total_count` = `high_count` + `low_count`
	Low Count	00000010
	Bypass Enable ¹⁴	00000001	`Data[0]` = bypass enable `Data[0]` = 1, bypass is enabled. The counter is bypassed with counter division value = 1.
	Odd Division ¹⁴	00000001	`Data[7]` = Odd division `Data[7]` = 0, odd division is disabled. The selected counter duty cycle = `high_count`/`total_count`. `Data[7]` = 1, odd division enabled. The selected counter duty cycle = (`high_count` – 0.5)/`total_count`.
`C1` Counter	High Count	00011111	`Data[7:0]` = `high_count` `Data[7:0]` = `low_count` `total_count` = `high_count` + `low_count`
	Low Count	00100010
	Bypass Enable ¹⁴	00100000	`Data[0]` = bypass enable `Data[0] = 1`, bypass is enabled. The counter is bypassed with counter division value = 1.
	Odd Division ¹⁴	00100001	`Data[7]` = Odd division `Data[7]` = 0, odd division is disabled. The selected counter duty cycle = `high_count`/`total_count`. `Data[7]` = 1, odd division enabled. The selected counter duty cycle = (`high_count` – 0.5)/`total_count`.
`C2` Counter	High Count	00100011	`Data[7:0]` = `high_count` `Data[7:0]` = `low_count` `total_count` = `high_count` + `low_count`
	Low Count	00100110
	Bypass Enable ¹⁴	00100100	`Data[0]` = bypass enable `Data[0]` = 1, bypass is enabled. The counter is bypassed with counter division value = 1.
	Odd Division ¹⁴	00100101	`Data[7]` = Odd division `Data[7]` = 0, odd division is disabled. The selected counter duty cycle = `high_count`/`total_count`. `Data[7]` = 1, odd division enabled. The selected counter duty cycle = (`high_count` – 0.5)/`total_count`.
`C3` Counter	High Count	00100111	`Data[7:0]` = `high_count` `Data[7:0]` = `low_count` `total_count` = `high_count` + `low_count`
	Low Count	00101010
	Bypass Enable ¹⁴	00101000	`Data[0]` = bypass enable `Data[0]` = 1, bypass is enabled. The counter is bypassed with counter division value = 1.
	Odd Division ¹⁴	00101001	`Data[7]` = Odd division `Data[7]` = 0, odd division is disabled. The selected counter duty cycle = `high_count`/`total_count`. `Data[7]` = 1, odd division enabled. The selected counter duty cycle = (`high_count` – 0.5)/`total_count`.
`C4` Counter	High Count	00101011	`Data[7:0]` = `high_count` `Data[7:0]` = `low_count` `total_count` = `high_count` + `low_count`
	Low Count	00101110
	Bypass Enable ¹⁴	00101100	`Data[0]` = bypass enable `Data[0]` = 1, bypass is enabled. The counter is bypassed with counter division value = 1.
	Odd Division ¹⁴	00101101	`Data[7]` = Odd division `Data[7]` = 0, odd division is disabled. The selected counter duty cycle = `high_count`/`total_count`. `Data[7]` = 1, odd division enabled. The selected counter duty cycle = (`high_count` – 0.5)/`total_count`.
`C5` Counter	High Count	00101111	`Data[7:0]` = `high_count` `Data[7:0]` = `low_count` `total_count` = `high_count` + `low_count`
	Low Count	00110010
	Bypass Enable ¹⁴	00110000	`Data[0]` = bypass enable `Data[0]` = 1, bypass is enabled. The counter is bypassed with counter division value = 1.
	Odd Division ¹⁴	00110001	`Data[7]` = Odd division `Data[7]` = 0, odd division is disabled. The selected counter duty cycle = `high_count`/`total_count`. `Data[7]` = 1, odd division enabled. The selected counter duty cycle = (`high_count` – 0.5)/`total_count`.
`C6` Counter	High Count	00110011	`Data[7:0]` = `high_count` `Data[7:0]` = `low_count` `total_count` = `high_count` + `low_count`
	Low Count	00110110
	Bypass Enable ¹⁴	00110100	`Data[0]` = bypass enable `Data[0]` = 1, bypass is enabled. The counter is bypassed with counter division value = 1.
	Odd Division ¹⁴	00110101	`Data[7]` = Odd division `Data[7]` = 0, odd division is disabled. The selected counter duty cycle = `high_count`/`total_count`. `Data[7]` = 1, odd division enabled. The selected counter duty cycle = (`high_count` – 0.5)/`total_count`.
`C7` Counter	High Count	00110111	`Data[7:0]` = `high_count` `Data[7:0]` = `low_count` `total_count` = `high_count` + `low_count`
	Low Count	00111010
	Bypass Enable ¹⁴	00111000	`Data[0]` = bypass enable `Data[0]` = 1, bypass is enabled. The counter is bypassed with counter division value = 1.
	Odd Division ¹⁴	00111001	`Data[7]` = Odd division `Data[7]` = 0, odd division is disabled. The selected counter duty cycle = `high_count`/`total_count`. `Data[7]` = 1, odd division enabled. The selected counter duty cycle = (`high_count` – 0.5)/`total_count`.
Charge Pump Current ¹⁴	Charge pump setting [2:0]	00000001	`Data[6:4]` = Charge Pump Setting [2:0] Configure charge pump setting [2:0] on data bit 4 to 6.
Charge Pump Current ¹⁴	Charge pump setting [5:3]	00001101	`Data[7:5]` = Charge Pump Setting [5:3] Configure charge pump setting [5:3] on data bit 5 to 7.
Bandwidth Setting ¹⁴	—	00001010	`Data[6:3]` = Bandwidth Setting Configure bandwidth setting on data bit 3 to 6.
Ripplecap Setting ¹⁴	—	00001010	`Data[2:1]` = Ripplecap Setting Configure ripplecap setting on data bit 1 and 2.
Calibration ¹⁴	Calibration Request	01001001	`Data[6]` = Request Calibration `Data[6]` = 1, to request calibration
Calibration ¹⁴	Calibration Enable	01001010	`Data[7:0]` = Enable Calibration `Data[7:0]` = 8’b00000011, to enable calibration

¹⁴ Perform a read-modify-write operation to configure this setting. PLL may lose lock and can cause reliability issue to your device if you configure with the wrong PLL setting, configure the wrong bit, or overwrite the whole byte for settings that made up just part of one byte.

6.5.1.1. Data Bus Setting for Bandwidth Control and Charge Pump

Table 19. I/O Bank I/O PLL Data Bus Setting for Bandwidth Control and Charge Pump (For Low Bandwidth)
Multiply Factor ¹⁵	Low Bandwidth
Multiply Factor ¹⁵	Bandwidth Control Setting Data [6:3]	Charge Pump Setting [2:0] Address = 00000001 Data [6:4]	Charge Pump Setting [5:3] Address = 00001101 Data [7:5]
4–5	4'b0011	3'b011	3'b000
6–7	4'b0011	3'b011	3'b000
8–10	4'b0011	3'b100	3'b000
11–15	4'b0100	3'b100	3'b000
16–20	4'b0101	3'b100	3'b000
21–23	4'b0101	3'b101	3'b000
24–43	4'b0110	3'b100	3'b000
44–64	4'b0111	3'b100	3'b000
65–85	4'b1000	3'b100	3'b000
86–124	4'b1010	3'b011	3'b000
125–160	4'b1010	3'b011	3'b000

Table 20. I/O Bank I/O PLL Data Bus Setting for Bandwidth Control and Charge Pump (For Medium Bandwidth)
Multiply Factor ¹⁵	Medium Bandwidth
Multiply Factor ¹⁵	Bandwidth Control Setting Data [6:3]	Charge Pump Setting [2:0] Address = 00000001 Data [6:4]	Charge Pump Setting [5:3] Address = 00001101 Data [7:5]
4–5	4'b0010	3'b110	3'b000
6–7	4'b0011	3'b101	3'b000
8–10	4'b0011	3'b101	3'b000
11–15	4'b0011	3'b110	3'b000
16–20	4'b0100	3'b110	3'b000
21–23	4'b0100	3'b111	3'b000
24–43	4'b0101	3'b110	3'b000
44–64	4'b0110	3'b110	3'b000
65–85	4'b0111	3'b110	3'b000
86–124	4'b1000	3'b110	3'b000
125–160	4'b1010	3'b100	3'b000

Table 21. I/O Bank I/O PLL Data Bus Setting for Bandwidth Control and Charge Pump (For High Bandwidth)
Multiply Factor ¹⁵	High Bandwidth
Multiply Factor ¹⁵	Bandwidth Control Setting Data [6:3]	Charge Pump Setting [2:0] Address = 00000001 Data [6:4]	Charge Pump Setting [5:3] Address = 00001101 Data [7:5]
4–5	4'b0010	3'b001	3'b001
6–7	4'b0010	3'b010	3'b001
8–10	4'b0010	3'b011	3'b001
11–15	4'b0011	3'b001	3'b001
16–20	4'b0011	3'b010	3'b001
21–23	4'b0100	3'b010	3'b001
24–43	4'b0100	3'b011	3'b001
44–64	4'b0101	3'b011	3'b001
65–85	4'b0101	3'b011	3'b001
86–124	4'b1001	3'b110	3'b000
125–160	4'b1001	3'b110	3'b000

Table 22. Fabric-Feeding I/O PLL Data Bus Setting for Bandwidth Control and Charge Pump (For Medium Bandwidth)
Multiply Factor ¹⁵	Medium Bandwidth
Multiply Factor ¹⁵	Bandwidth Control Setting Data [6:3]	Charge Pump Setting [2:0] Address = 00000001 Data [6:4]	Charge Pump Setting [5:3] Address = 00001101 Data [7:5]
4–5	4'b0011	3'b100	3'b000
6–7	4'b0100	3'b100	3'b000
8–10	4'b0101	3'b100	3'b000
11–15	4'b0110	3'b100	3'b000
16–20	4'b0111	3'b100	3'b000
21–23	4'b0111	3'b100	3'b000
24–43	4'b1001	3'b011	3'b000
44–64	4'b1010	3'b011	3'b000
65–85	4'b1010	3'b100	3'b000
86–104	4'b1010	3'b101	3'b000
105–140	4'b1011	3'b100	3'b000
141–160	4'b1011	3'b100	3'b000

Table 23. Fabric-Feeding I/O PLL Data Bus Setting for Bandwidth Control and Charge Pump (For High Bandwidth)
Multiply Factor ¹⁵	High Bandwidth
Multiply Factor ¹⁵	Bandwidth Control Setting Data [6:3]	Charge Pump Setting [2:0] Address = 00000001 Data [6:4]	Charge Pump Setting [5:3] Address = 00001101 Data [7:5]
4–5	4'b0010	3'b001	3'b001
6–7	4'b0011	3'b000	3'b001
8–10	4'b0011	3'b000	3'b001
11–15	4'b0100	3'b000	3'b001
16–20	4'b0110	3'b110	3'b000
21–23	4'b0111	3'b101	3'b000
24–43	4'b1000	3'b101	3'b000
44–64	4'b1001	3'b101	3'b000
65–85	4'b1001	3'b110	3'b000
86–104	4'b1001	3'b110	3'b000
105–140	4'b1010	3'b101	3'b000
141–160	4'b1010	3'b101	3'b000

¹⁵ If you select the Use Nondedicated Feedback Path option under the Normal or Source Synchronous compensation mode, the Multiply Factor is M x C _i, where M is M counter value while C _i is the Compensated Outclk C counter value. Else, the Multiply Factor is only the M counter value.

6.5.1.2. Data Bus Setting for Ripplecap

Table 24. I/O Bank I/O PLL Data Bus Setting for Ripplecap
Multiply Factor ¹⁶	Ripplecap Setting Address = 00001010 Data [2:1]
Multiply Factor ¹⁶	Low Bandwidth	Medium Bandwidth	High Bandwidth
4–5	2'b01	2'b01	2'b00
6–7	2'b11	2'b01	2'b01
8–10	2'b11	2'b01	2'b01
11–15	2'b11	2'b01	2'b01
16–20	2'b11	2'b01	2'b01
21–23	2'b11	2'b01	2'b01
24–43	2'b11	2'b01	2'b01
44–64	2'b11	2'b01	2'b01
65–85	2'b11	2'b01	2'b01
86–124	2'b11	2'b01	2'b01
125–160	2'b11	2'b01	2'b01

Table 25. Fabric-Feeding I/O PLL Data Bus Setting for Ripplecap
Multiply Factor ¹⁶	Ripplecap Setting Address = 00001010 Data [2:1]
Multiply Factor ¹⁶	Medium Bandwidth	High Bandwidth
4–5	2'b01	2'b00
6–7	2'b01	2'b00
8–10	2'b01	2'b01
11–15	2'b01	2'b01
16–20	2'b01	2'b01
21–23	2'b01	2'b01
24–43	2'b01	2'b01
44–64	2'b01	2'b01
65–85	2'b01	2'b01
86–104	2'b01	2'b01
105–140	2'b01	2'b01
141–160	2'b01	2'b01

¹⁶ If you select the Use Nondedicated Feedback Path option under the Normal or Source Synchronous compensation mode, the Multiply Factor is M x C _i, where M is M counter value while C _i is the Compensated Outclk C counter value. Else, the Multiply Factor is only the M counter value.

6.5.2. Output Clock and the Corresponding Data Bit Setting for Clock Gating Reconfiguration

Table 26. Output Clock and the Corresponding Data Bit Setting for Clock Gating Reconfiguration
Output Clock	Data Bus Bit Setting (Binary)
`C1`	`data[0]`	Gated = 1'b0 Ungated = 1'b1
`C2`	`data[1]`
`C3`	`data[2]`
`C4`	`data[3]`
`C5`	`data[4]`
`C6`	`data[5]`
`C7`	`data[6]`

6.5.3. Data Bus Setting for Dynamic Phase Shift for IOPLL Reconfig IP Core

Table 27. Data Bus Setting for Dynamic Phase Shift for IOPLL Reconfig IP Core

Write Data Bus Setting

Description

data[2:0]

Determines the number of phase shifts per dynamic phase shift operation. Up to seven phase shifts per operation are possible. Each phase shift step is equal to 1/8 of I/O PLL VCO period.

data[3]

Determines the direction of dynamic phase shift. When data[3] = 0, phase shift is in negative direction. When data[3] = 1, phase shift is in positive direction.

data[7:4]

Determines the counter to be selected to perform dynamic phase shift operation.

Counter Name	data[7:4]
`C1`	4’b0001
`C2`	4’b0010
`C3`	4’b0011
`C4`	4’b0100
`C5`	4’b0101
`C6`	4’b0110
`C7`	4’b0111
All `C` counters	4’b1111

6.6. Design Example

This design example uses a AGFB014R24A2E3VR0 device to demonstrate the implementation of the following three different I/O PLL reconfiguration options using the IOPLL Reconfig IP core:

.mif streaming reconfiguration
Advanced mode reconfiguration
Clock gating reconfiguration

You must install the Intel^® Quartus^® Prime software version 20.1 or later. The software must be installed on a Windows* or Linux* computer that meets the Intel^® Quartus^® Prime software minimum requirements.

This design example consists of the IOPLL IP core, IOPLL Reconfig IP core, In-System Sources & Probes Intel^® FPGA IP core, and Reset Release Intel FPGA IP core.

Before reconfiguration, the I/O PLL synthesizes two output clocks of 150 MHz and 300 MHz on counter C1 and counter C2 output, respectively, at medium bandwidth. The input reference clock is 100 MHz.

The IOPLL Reconfig IP core connects to a state machine to perform I/O PLL reconfiguration operation. A high pulse on the reset_SM signal triggers the I/O PLL reconfiguration operation. The desired reconfiguration mode can be selected through mode_0 and mode_1 inputs. These inputs are controlled through the In-System Sources & Probes IP core.

Table 28. Reconfiguration Mode Selection for the Design Example
Reconfiguration Mode	mode_1	mode_0
.mif streaming reconfiguration	0	0
Advanced mode reconfiguration	0	1
Clock gating reconfiguration	1	0

Download and restore the Design Example (iopll-reconfig.qar) file. Change the device and pin assignments of the design example to match your hardware. Ensure MIF file path in the IOPLL Reconfig IP core is set to the .mif file path in the project of the design example. Recompile the design example and ensure that the design example does not contain any timing violation after reconfiguration

6.6.1. Reconfiguration Option: .mif Streaming Reconfiguration Using IOPLL Reconfig IP Core

After the I/O PLL reconfiguration operation is complete, the I/O PLL operates in the following configuration at medium bandwidth:

400 MHz with 0 ps phase shift on counter C1 output
200 MHz with 0 ps phase shift on counter C2 output

To run the design example using .mif streaming reconfiguration, perform these steps:

Open AN.stp file and program the device top.sof.
In the In-System Sources & Probes IP core parameter editor, ensure the mode_0 and mode_1 inputs remain in low pulse.
Assert a high pulse on the reset_SM signal to start the I/O PLL reconfiguration operation.

Figure 26. Waveform Example for .mif Streaming Reconfiguration Design Example

6.6.2. Reconfiguration Option: Advanced Mode Reconfiguration and Recalibration Using IOPLL Reconfig IP Core

After the I/O PLL reconfiguration operation is complete, the I/O PLL operates in the following configuration at medium bandwidth:

400 MHz with 0 ps phase shift on counter C1 output
200 MHz with 0 ps phase shift on counter C2 output

The state machine initiates the I/O PLL recalibration process when the I/O PLL reconfiguration operation is complete.

To run the design example using advanced mode reconfiguration, perform these steps:

Open AN.stp file and program the device top.sof.
In the In-System Sources & Probes IP core, assert mode_0 to high pulse and mode_1 remains low.
Assert a high pulse on the mgmt_reset signal to reset the IOPLL Reconfig IP core.
Assert a high pulse on the reset_SM signal to start the I/O PLL reconfiguration operation.

Figure 27. Waveform Example for Advanced Mode Reconfiguration Design Example

6.6.3. Reconfiguration Option: Clock Gating Reconfiguration Using IOPLL Reconfig IP Core

After the I/O PLL reconfiguration operation is complete, the I/O PLL operates in the following configuration at medium bandwidth:

Counter C1 output is ungated
Counter C2 output is gated

To run the design example using clock gating reconfiguration, perform these steps:

Open AN.stp file and program the device top.sof.
In the In-System Sources & Probes IP core, keep mode_0 in low pulse and assert mode_1 to high pulse.
Assert a high pulse on the reset_SM signal to start the I/O PLL reconfiguration operation.

Figure 28. Waveform Example for Clock Gating Reconfiguration Design Example

7. Intel Agilex Clocking and PLL User Guide Archives

If the table does not list a software version, the user guide for the previous software version applies.

Intel^® Quartus^® Prime Version	User Guide
20.1	Intel Agilex Clocking and PLL User Guide
19.3	Intel Agilex Clocking and PLL User Guide

8. Document Revision History for the Intel Agilex Clocking and PLL User Guide

Document Version	Intel^® Quartus^® Prime Version	Changes
2021.09.21	20.3	Updated the description in the Root Clock Gate section. Added a note in the PLL Architecture section. Added description on PLL loses lock in the Locked section. Updated the Manual Switchover mode description for the Switchover Mode parameter in the IOPLL IP Core Parameters - Settings Tab for Intel^® Agilex™ Devices table. Updated the address for `C1` to `C7` counters in the Address Bus and Data Bus Settings for Advanced Mode Reconfiguration table. Updated `data[7:4]` for `C1` to `C7` counters in the Data Bus Setting for Dynamic Phase Shift for IOPLL Reconfig IP Core table. Updated `mgmt_writedata[7..0]` signal in the Waveform Example for Advanced Mode Reconfiguration Design Example diagram. Updated `mgmt_writedata[7..0]` signal in the Waveform Example for Clock Gating Reconfiguration Design Example diagram.
2021.06.21	20.3	Updated the PLL Locations section.
2021.03.29	20.3	Added table: Spread-Spectrum Input Clocking Supported Profile. Added guideline: Guideline: Achieving 5% Duty Cycle for f_{OUT_EXT} ≥ 300 MHz Using `tx_outclk` Port from LVDS SERDES Intel^® FPGA IP . Updated the IOPLL Reconfig Intel^® FPGA IP Core Current Release Information table.
2020.09.28	20.3	Updated the note to the spread-spectrum input clock tracking feature in the PLL Features in Intel^® Agilex™ Devices table. Added the IP-XACT File Generation section under IOPLL Intel^® FPGA IP Core. Updated the Charge Pump Setting [2:0] value for Multiple Factor 141–160 in the Fabric-Feeding I/O PLL Data Bus Setting for Bandwidth Control and Charge Pump (For High Bandwidth) table. Updated the high bandwidth ripplecap setting for Multiply Factor 141–160 in the Fabric-Feeding I/O PLL Data Bus Setting for Ripplecap table. Updated C counters in the following sections: I/O Bank I/O PLL High-Level Block Diagram for Intel^® Agilex™ Devices Fabric-Feeding I/O PLL High-Level Block Diagram for Intel^® Agilex™ Devices Address Bus and Data Bus Settings for Advanced Mode Reconfiguration table Output Clock and the Corresponding Data Bit Setting for Clock Gating Reconfiguration table Data Bus Setting for Dynamic Phase Shift for IOPLL Reconfig IP Core table
2020.04.13	20.1	Updated the Examples of Clock Networks Sizes Using Intel^® Agilex™ Programmable Clock Routing diagram. Removed zero-delay buffer compensation support for fabric-feeding I/O PLL in the following sections: PLL Features in Intel^® Agilex™ Devices table Fabric-Feeding I/O PLL High-Level Block Diagram for Intel^® Agilex™ Devices diagram Added description for top and bottom sub-banks in the PLL Locations section. Updated the I/O PLL Locations in I/O Bank diagram. Updated the Zero-Delay Buffer Mode section. Mentioned that the ZDB mode is only supported for I/O bank I/O PLL. Added description about the bidirectional I/O pin must not be globally promoted. Added information on IOPLL Reconfig IP ports in the PLL Reconfiguration and Dynamic Phase Shift section. Moved the information from the IOPLL Reconfig Intel^® FPGA IP Core section. Added a note to zero delay buffer for Compensation Mode in the IOPLL IP Core Parameters - PLL Tab for Intel^® Agilex™ Devices table. Added description on supported output clocks and `C` counters in the IOPLL IP Core Parameters - Advanced Parameters Tab for Intel^® Agilex™ Devices table. Added a design example with three reconfiguration options using IOPLL Reconfig Intel^® FPGA IP core.
2019.12.18	19.3	Removed `scanclk` signal in the Guideline: I/O PLL Reconfiguration section.
2019.10.31	19.3	Added the Examples of Clock Networks Sizes Using Intel^® Agilex™ Programmable Clock Routing diagram in the Programmable Clock Routing section. Updated the number of resources available in the Programmable Clock Routing Resources for Intel^® Agilex™ Devices table. Updated the PLL Features in Intel^® Agilex™ Devices table. Updated `C` counter divide factor range from '1 to 510' to '1 to 512'. Added a note to dedicated external clock outputs. Removed the following PLL features for fabric-feeding I/O PLL. Dedicated external clock outputs External feedback input pin External feedback compensation Added spread-spectrum input clock tracking feature. Updated the PLL Usage section. Removed external feedback mode in the Fabric-Feeding I/O PLL High-Level Block Diagram for Intel^® Agilex™ Devices diagram. Clarified that EFB mode is only supported for I/O bank I/O PLL. Updated the PLL Cascading section. Added description that Intel^® Agilex™ devices does not support I/O PLL cascading within the same I/O bank. Updated `outclk[8:0]` to `outclk[6:0]` in the I/O-PLL-to-I/O-PLL cascading diagrams. Added the following guidelines: Guideline: I/O PLL Reconfiguration Clocking Constraints IP Core Constraints Added information for the following IP cores: Clock Control Intel^® FPGA IP version 1.0.0 IOPLL Intel^® FPGA IP version 19.3.0 IOPLL Reconfig Intel^® FPGA IP version 19.3.0
2019.04.02	—	Initial release.

Pre-Scale Counter, N and Multiply Counter, M

Post-Scale Counter, C

Integer Mode

Pre-Scale Counter, `N` and Multiply Counter, `M`

Post-Scale Counter, `C`