Cyclone III FPGA Interface and Protocol Support

Cyclone® III FPGAs support serial, bus, and network interfaces, as well as a wide range of communications protocols. These interfaces and protocols are commonly used in many industrial, communications, and an increasing number of consumer applications.

Altera offers a variety of intellectual property (IP) cores for these protocols that are optimized for the Cyclone III FPGA architecture.

Consumer Digital Display Standards

FPD–Flat panel display (FPD) link is a National Semiconductor-defined LVDS-based link between a host panel and display panel in an LCD monitor and television platform. Cyclone III FPGAs are predominantly placed at the receive-end of the FPD link to meet the maximum data rate requirement of 805 Mbps. A single FPD link channel consists of four LVDS data pairs and a source-synchronous clock pair, and Cyclone III FPGAs support up to two such channels.

RSDS–Reduced swing differential signaling (RSDS) is a National Semiconductor defined signaling standard primarily used for display applications with resolutions between video graphics arrays (VGAs) and ultra extended graphic arrays (UXGAs). It is a chip-to-chip protocol and links the flat-panel timing controllers to the column drivers. RSDS is a differential interface with a nominal swing of 200mV that retains the many benefits of the LVDS interface for a high-bandwidth, robust digital interface.

PPDS– Point to point differential signaling (PPDS) is a National Semiconductor defined signaling standard used for LCD displays that simplifies the interconnect to improve display performance, enable smaller bezels, and adding other features.

Flat Link–Flat Link is a Texas Instruments-defined LVDS-based link between a host panel and display panel in an LCD monitor and television platform. This interface is similar to that of FPD link, and is primarily used by Philips and Thomson. Cyclone III FPGAs are predominantly placed at the transmit-end of the Flat Link to meet the maximum data rate requirement of 622 Mbps and can be used on the receiver-side as well.

mini-LVDS–mini-LVDS is a Texas Instruments-defined interface similar to RSDS and meets the same needs. The requirements for mini-LVDS interfaces are identical to that of RSDS, except in the AC timing requirements. mini-LVDS assumes a center-aligned output clock.

Cyclone III FPGAs can enable you to effectively implement these protocols with features such as on-chip termination (OCT) allowing you to drive multiple signals and ease board layout and reliability.

PCI Express

PCI Express is rapidly establishing itself as the successor to PCI, providing higher performance, increased flexibility, and scalability for next-generation systems without increasing costs, all while maintaining software compatibility with existing PCI applications. Cyclone III FPGAs are an effective way to quickly implement a PCI Express link and take advantage of the increased scalable bandwidth it provides. You can easily design high-volume, low-cost PCI Express x1 solutions today with Cyclone III FPGAs and external PHY transceivers.
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The PCI local bus is a high-performance 32-bit or 64-bit bus with multiplexed address and data lines. The bus provides a processor-independent data path between highly integrated peripheral controller components, peripheral add-in boards, and processor/memory systems. The Cyclone III FPGA PCI system interface is designed to be compatible with the 3.3-V PCI Local Bus Specification (Rev. 2.2) and meets 64-bit/66-MHz operating frequency and timing requirements. The I/O elements in Cyclone III FPGAs are specifically designed to meet the strict PCI set-up and hold time requirements. To provide maximum flexibility, each input signal can go through two separate delay paths feeding different areas of the device.


Since the introduction of the 66-MHz PCI Local Bus Specification in 1994, bandwidth requirements of peripheral devices have grown steadily. The preferred approach to moving beyond today’s PCI Local Bus Specification is to enhance it. PCI-X enables the design of systems and devices that can operate at speeds significantly higher than today’s specification allows. Just as importantly, it provides backward compatibility by allowing devices to operate at conventional PCI frequencies and modes when installed in conventional systems. This high degree of backward compatibility enables the easy migration of systems and devices to bandwidth in excess of 1 gigabit per second (Gbps). Cyclone III FPGAs meet both the 33-MHz and the 66-MHz protocols and timing requirements of PCI and the timing requirements of PCI-X up to 100 MHz.

Table 1 lists the required PCI bus operation modes when devices of various PCI standards are used.

Table 1. PCI and PCI-X Interoperability

Device(s) on Bus Operation Mode of Bus
One or More 33-MHz PCI DeviceConventional 33-MHz Mode
Only 66-MHz PCI DevicesConventional 33-MHz or 66-MHz Mode
Only PCI-X DevicesPCI-X Mode
One or More PCI-X 66-MHz DeviceMaximum Clock Frequency of 66 MHz
Only PCI-X 100-MHz DevicesMaximum Clock Frequency of 100 MHz

SDRAM and SRAM Interfaces

SDRAM and SRAM devices are used broadly in applications including PCs, consumer electronics, communications, and networking for data storage. Cyclone III FPGAs are designed to communicate with single data rate (SDR) and double data rate (DDR) and DDR2 SDRAM, as well as QDRII SRAM devices through a dedicated interface that ensures fast, reliable data transfers. New improvements to the Cyclone III FPGA architecture allow you to easily implement these memory interfaces and meet timing requirements such as dynamic phase alignment. Details are available on the External Memory Interfaces page in the Cyclone III Devices section of this website.

10/100 and Gigabit Ethernet

Ethernet is the most widely used local area network (LAN) access method and is defined by the IEEE 802.3 Standard. Cyclone III FPGAs can be used to implement the Ethernet media access controller (MAC) and can be interfaced with physical layer (PHY) devices at a maximum bandwidth of 10 Mbps, 100 Mbps, or 1 Gbps. Together with Cyclone III device-optimized IP cores, you can integrate an Ethernet MAC function into a Cyclone III FPGA in minutes. Details are available on the Altera's Gigabit Ethernet Solutions page.

Serial Bus Interfaces

Cyclone III FPGAs support a variety of serial bus interfaces such as serial peripheral interface (SPI), inter-integrated circuit (I2C), IEEE 1394 Standard, and universal serial bus (USB) (shown in Table 2).

Table 2. Serial Bus Interface Support in Cyclone III Devices

Protocol SPI I2C IEEE 1394 USB 2.0
Maximum Bandwidth (Mbps) (1) 13.4400480

Note to Table 2:

  1. Maximum bandwidth is equal to or greater than the data rate.

The SPI and I2C standards can be implemented in Cyclone III FPGAs to provide low-speed communication links between integrated circuits, processors and peripherals. The IEEE 1394 and USB standards provide connections between processors, computers, and other devices. Cyclone III FPGAs can be used to implement the bus controllers and interface with the PHY devices. All these serial bus interfaces are typically used in price-sensitive consumer products. The Cyclone III device family provides an ideal low-cost solution for implementing the standards and custom functions in these applications.

Communications Protocols

Cyclone III FPGAs support various communication protocols including E1, E3, T1, T3, and SONET/SDH protocols (Table 3).

Table 3. Communications Protocol Support in Cyclone III FPGAs

Protocol E1 E3 T1 T3 OC-1/
Maximum Bandwidth (Mbps) (1)2.04834.3681.54444.73651.84155.52622.082,488

Note to Table 3:

  1. Maximum bandwidth is equal to or greater than the data rate.

E1 and E3 are the European standards for digital transmission; T1 and T3 are the corresponding North American standards for digital transmissions. SONET/SDH standards provide data transmission over fiber optics. Cyclone III FPGAs can be used to implement the framers of all these protocols and connect to the transceiver devices.

Cyclone III FPGAs can also be used to implement the POS-PHY and UTOPIA communications interface protocols shown in Table 4.

Table 4. Communications Interface Protocol Support in Cyclone III FPGAs

Protocol POS-PHY
Level 2
Level 3
Level 2
Level 3
Maximum Bandwidth (Mbps) (1)6222,4886222,488
Bus Width168/328/168/16/32

Note to Table 4:

  1. Maximum bandwidth is greater than the data rate.

POS-PHY and UTOPIA protocols provide physical and link layer interfaces for SONET/SDH and asynchronous transfer mode (ATM) respectively. These protocols and interfaces can be implemented in Cyclone III FPGAs.

These communications and interface protocols are used in low-end and mid-range communications equipment. Cyclone III FPGAs provide the performance, logic density, and system features required to support these applications.