FPGAs get tune-up for high-speed protocols
By Michael Santarini, Senior Editor -- EDN, February 16, 2006
Altera has added a family of devices for high-speed protocols to its top-of-the line Stratix II FPGA. The Stratix II GX family targets the sweet spot of high-speed protocols, according to David Greenfield, senior director of high-density-FPGA-product marketing. The devices support PCI Express, SDI (serial-digital-interface), XAUI (extended-auxiliary-unit-interface), SONET (synchronous-optical-networking), Gigabit Ethernet, SerialLite II, Serial RapidIO, and CEI-6G-LR/SR (Common Electrical Interface 6-Gbps long-reach/short-reach) protocols. To create the GX devices, Altera replaced the I/O along one edge of a 90-nm Stratix II floorplan with a bank of transceivers. Doing so allows Altera to offer GX devices with as many as 20 transceivers, each operating at 622 Mbps to 6.375 Gbps. A top-of-the-line GX device also has 132,540 logic elements, or roughly 2 million ASIC gates, and 6.7 Mbits of embedded memory.
Each transceiver's receiver channel features a synchronizer, a 8b/10b decoder, a word aligner, a rate matcher, and an equalizer CDR (clock-and-data-recovery) demultiplexer. The transmitter channel offers an 8b/10b encoder and multiplexer pre-emphasis. Clock-management circuitry links the channels. Altera based these choices on the percentage of transceiver customers who are likely to use a block, according to Greenfield. Although 8b/10b encoding and decoding are easy to do in soft or hard logic, Altera puts it into hard IP (intellectual property) because almost every transceiver customer will use it, he says. For XAUI, the company implemented a state machine in hard IP but used soft IP for the standard MAC (media-access-controller) function.
Users furnish Altera with S-parameters, and the company's application engineers use the program to create, in about 45 minutes, optimal settings for equalization and other variables. The GX family will become available for sampling early this year, and volume prices will start at $49 for the EP2SGX30CF780 device.
Altera Corp, www.altera.com.
