Intel® FPGA IP allows you to dynamically calibrate I/O with reference to
an external resistor. The OCT IP improves
signal integrity, reduces board space, and is necessary for communicating with external
devices such as memory interfaces.
The OCT IP is available for
Arria® 10, and
Cyclone® 10 GX devices. If you are migrating designs from
Arria® V, and
Cyclone® V devices, you need to migrate the IP. For more
details, refer to the related information.
Support for up to 12 on-chip termination (OCT) blocks
Support for calibrated on-chip series termination
(RS) and calibrated on-chip parallel termination (RT) on
all I/O pins
Calibrated termination values of 25 Ω and 50 Ω
Support for OCT calibration in power-up and user modes
OCT Intel FPGA IP Overview
Figure 1. OCT IP Top-Level
DiagramThis figure shows the top-level diagram of the OCT IP.
Table 1. OCT IP
When used with OCT, the pin connects to an external reference
resistor to calculate the calibration codes to implement the
Generates and sends calibration code words to the I/O buffer
Receives the calibration code words serially from the OCT block and
sends the calibration code words in parallel to the buffers.
Each OCT block has one RZQ pin.
RZQ pins are dual-purpose pins. If the pins are not connected to the OCT block, you
can use the pins as regular I/O pins.
Calibrated pins must have the same VCCIO voltage as the OCT block and the
RZQ pin. Calibrated pins connected to the same OCT block must have the same series
and parallel termination values.
You can apply location constraints on the RZQ pins to determine the placement of the
OCT block because the RZQ pin can only be connected to its corresponding OCT
The OCT block is a component that generates calibration codes to terminate the
During calibration, the OCT matches the impedance seen on the external resistor through the
rzqin port. Then, the OCT block generates two 16-bit calibration
code words—one word calibrates the series termination and the other word calibrates the
parallel termination. A dedicated bus sends the words serially to the OCT logic.
The OCT block sends the calibration code words serially to the OCT logic through
the ser_data ports.
The enser signal, when triggered, specifies
from which OCT block to read the calibration code words. The calibration code words are
then buffered into the serial-to-parallel shift logic. After that, the s2pload signal automatically asserts to send the calibration
code words in parallel to the I/O buffers.
The calibration code words activate or deactivate the transistors in the I/O block, which
will emulate series or parallel resistance to match the impedance.
Figure 2. Internals of OCT Logic
OCT Intel FPGA IP Functional Description
To meet DDR memory specification,
Arria® 10, and
Cyclone® 10 GX
devices support on-chip series termination (RS OCT) and
on-chip parallel termination (RT OCT) for single-ended I/O
standards. OCT can be supported on any I/O bank. The VCCIO
must be compatible for all I/Os in a given bank.
Arria® 10, or
Cyclone® 10 GX device, there is one OCT block in each
I/O bank. Each OCT block requires an association with an external 240 Ω reference resistor through an RZQ pin.
The RZQ pin shares the same VCCIO supply with the I/O bank where the pin is located. An RZQ pin is a dual function I/O pin that you can use as a regular I/O if you do not use OCT calibration. When you use the RZQ pin for OCT calibration, the RZQ pin connects the OCT block to ground through an external 240 Ω resistor.
The following figures show how OCTs are connected in a single I/O column (in a daisy chain). An OCT can calibrate an I/O belonging to any bank, provided that the bank is in the same column and meets the voltage requirements. Because there are no connections between columns, OCT can only be shared if the pins belong to the same I/O column of the OCT.
Figure 3. OCT Bank-to-Bank Connections
Figure 4. I/O Columns in
Quartus® Prime Pin PlannerThis figure is an example. The layout varies between different
Arria® 10, or
Cyclone® 10 GX devices.
Power-Up Mode Interfaces
The OCT IP in power-up mode
has two main interfaces:
One input interface connecting the FPGA RZQ pad to
the OCT block
Two 16-bit words output which connect to I/O
Figure 5. OCT Interfaces
User Mode OCT
User mode OCT operates the same way as power-up OCT mode, with the addition of
Figure 6. FSM SignalsThis figure shows a finite state machine (FSM) in the core controls the dedicated user
signals on the OCT block. The FSM ensures that the OCT block calibrates or sends
controlling code words as per your request.
The Fitter does not infer a user-mode OCT. If you want your OCT block to use the
user mode OCT feature, you must generate the OCT IP. However, because of hardware limitations, you
can only use one OCT IP in user
mode OCT in your design.
Note: A single OCT IP can control up to 12 OCT blocks.
The FSM provides the following signals:
Note: These signals are only available in user-mode and not power-up mode.
When you set the calibration_request vector, the FSM moves from IDLE state to CAL state. Keep the calibration_request vector at its value for two clock cycles. After two clock cycles, the FSM contains a copy of the vector. You must reset the vector to avoid reinitiating the calibration process.
During this state, the FSM checks which bits in the calibration_request vector were asserted and services them. The corresponding OCT blocks starts the calibration process that takes around 2,000 clock cycles to complete. After calibration completes, the calibration_busy signal is released.
Check Mask bit
The FSM checks each bit in the vector if the bit is set or not.
Shift Mask bit
This state simply loops over all the bits in the vector until it hits a
This state serially sends the termination code from the OCT block to the
termination logic. It takes 32 cycles to complete the transfer. After
each transfer, the FSM check for any pending bits in the vector and
services them accordingly.
Update Pending Bit
The pending register holds bits that corresponds to every
OCT block in the OCT
Intel® FPGA IP. This state updates the pending
register by resetting the serviced request.
When the calibration_shift_busy signal is
deasserted, you can assert s2pload
automatically asserts to transfer the new termination codes into the
buffers. The s2pload signal asserts
for at least 25 ns.
Because of hardware limitations, you cannot request another
calibration until all bits in
calibration_shift_busy vector are low.
OCT Intel FPGA IP Design Example
The OCT IP can
generate a design example that matches the same configuration chosen for the
The design example is a simple design that does not target any specific
application. You can use the design example as a reference on how to instantiate the
To generate the design example files, turn on the Generate Example Design option in the Generation dialog box during IP generation.
Note: The OCT IP does not support VHDL generation.
The software generates the <instance>_example_design directory along with
the IP, where <instance> is the name of
The <instance>_example_design directory
contains the make_qii_design.tcl scripts.
Note: The .qsys files are for internal use during design example generation only. You cannot edit the files.
Generating the Intel Quartus Prime Design Example
The make_qii_design.tcl script generates a synthesizable design example along with an
Quartus® Prime project, ready for compilation.
To generate synthesizable design example, follow these steps.
After generating the IP together with the design example files,
run the following script at the command prompt: quartus_sh -t make_qii_design.tcl.
If you wan to specify an exact device to use, use the following command: quartus_sh -t make_qii_design.tcl <device_name>.
The script generates a qii directory that contains the
ed_synth.qpf project file. You can open and compile this
project in the
Quartus® Prime software.
OCT Intel FPGA IP References
OCT Intel FPGA IP Parameter Settings
Table 3. OCT IP
Number of OCT blocks
1 to 12
Specifies the number of OCT blocks to be
generated. The default value is
Use backwards-compatible port names
Check this to use legacy top-level names compatible with
the ALTOCT IP. This
parameter is disabled by default.
Specifies whether OCT is user-controllable or not. The
default value is Power-up.
OCT block x calibration mode
Specifies the calibration mode for the OCT. X
corresponds to the number of the OCT block. The default value is
OCT Intel FPGA IP Signals
Table 4. Input Interface Signals
Input connection from RZQ pad to the OCT block. RZQ pad is connected to an external resistance. The OCT block uses impedance connected to the rzqin port as a reference to generate the calibration code.
This signal is available for power-up and user modes.
Input clock for user mode OCT. The clock must be 20 MHz or less.
Input reset signal. Reset is synchronous.
Input vector for [NUMBER_OF_OCT:0].
Every bit corresponds to an OCT block. When a bit is set to 1, the corresponding OCT calibrates, then
serially shift the code word into the termination logic block. The
request has to be held for two clock cycles. Due to hardware
limitations, you must wait until the calibration_shift_busy vector to be zero until another
request is issued; otherwise your request will not be processed.
Output vector for [NUMBER_OF_OCT:0] indicating which OCT block is currently working on calibration and shifting termination codes to the termination logic block. When a bit is 1, it indicates that an OCT block is calibrating and shifting the code word to the termination logic block.
Output vector for [NUMBER_OF_OCT:0] indicating which OCT block is currently working on calibration. When a bit is 1, it indicates that an OCT block is calibrating
16-bit output signal, with <x> ranging from 0 to 11. This signal connects to the seriesterminationcontrol port on the input/output buffer. This port sends the series termination code that calibrates Rs.
16-bit output signal, with <x> ranging from 0 to 11. This signal connects to the parallelterminationcontrol port on the input/output buffer. This port sends the parallel termination code that calibrates Rt.
Arria® 10, and
Cyclone® 10 GX devices have the following termination-related
Quartus® Prime settings file (.qsf) assignments:
Table 5. QSF Assignments
The input/output termination assignment specifies the termination value in
ohm on the pin in question.
To enable the series/parallel termination ports, include these
assignments, which specify the series and parallel termination
values for the pins.
Make sure to connect the seriesterminationcontrol
and parallelterminationcontrol ports from the OCT
Intel® FPGA IP to the GPIO
Intel® FPGA IP.
set_instance_assignment -name INPUT_TERMINATION "PARALLEL <VALUE> OHM WITH CALIBRATION" -to <pin>
set_instance_assignment -name OUTPUT_TERMINATION "SERIES <VALUE> OHM WITH CALIBRATION" -to <pin>
Directs the Fitter to make the proper connection from the desired OCT
block to the specified pins. This assignment is useful when I/O
buffers are not explicitly instantiated and you need to associate
the pins with a specific OCT block.
set_instance_assignment -name TERMINATION_CONTROL_BLOCK <desired OCT BLK> -to <pin name>
This assignment is supported in
Arria® 10, and
Cyclone® 10 GX devices only. This assignment creates an
without modifying the RTL.
The Fitter searches for the rzq pin name
in the netlist. If the pin does not exist, the Fitter creates the
pin name along with the OCT IP and its corresponding
connections. This allows you to create a group of pins to be
calibrated by an existing or non-existing OCT and the Fitter ensures
the legality of the design.
Termination can exist on input and output buffers, and sometimes simultaneously.
There are two methods to associate pin groups with an OCT block:
Use a .qsf assignment to
indicate which pin (bus) is associated with which OCT block. You can use the
RZQ_GROUPassignment. The former assignment associates a pin with an
OCT instantiated in the RTL while the latter associates the pin with a newly created
OCT without modifying the RTL.
Instantiate the I/O buffer primitives at the top
level and connect them to the appropriate OCT blocks.
Note: All I/O banks with the same VCCIO can share one OCT block even if that
particular I/O bank has its own OCT block. You can connect any number of I/O pins that
support calibrated termination to an OCT block. Ensure that you connect I/Os with
compatible configuration to an OCT block. You must also ensure that the OCT block and
its corresponding I/Os have the same VCCIO and series or parallel termination
values. With these settings, the Fitter places the I/Os and OCT block in the same
Quartus® Prime software generates warning messages if there is
no pin connected to the block.
IP Migration Flow for Arria V, Cyclone V, and Stratix V Devices
The IP migration flow allows you to migrate the ALTOCT IP of
Cyclone® V, and
devices to the OCT
Intel® FPGA IP of
Arria® 10, or
Cyclone® 10 GX devices.
The IP migration flow configures the OCT IP to match the settings of the ALTOCT IP, allowing you to regenerate the
Note: This IP supports the IP migration
flow in single OCT calibration mode only. If you are using double or POD calibration
mode, you do not need to migrate the IP.
Migrating Your ALTOCT IP to the OCT Intel FPGA IP
To migrate your ALTOCT IP to the
OCT IP, follow these steps:
Open your ALTOCT
IP in the IP Catalog.
In Currently selected device
family, select Stratix 10, Arria 10, or Cyclone
Click Finish to open the
OCT IP in the
The parameter editor configures the OCT IP settings similar to the
If there are any incompatible settings between the two, select new supported
Click Finish to
regenerate the IP.
Replace your ALTOCT IP instantiation in RTL with the OCT IP.
Note: The OCT IP port names may not match the ALTOCT IP port names. Therefore, simply
changing the IP name in the instantiation is not sufficient.
OCT Intel FPGA IP User Guide Archives
If an IP core version is not listed, the user guide for the previous IP core