field-programmable gate array
<hardware> (FPGA) A gate array where the logic network can be programmed
into the device after its manufacture. An FPGA consists of an array of logic
elements, either gates or lookup table RAMs, flip-flops and programmable
Most FPGAs are reprogrammable, since their logic functions and interconnect are
defined by RAM cells. The Xilinx LCA, Altera FLEX and AT&T ORCA devices are
examples. Others can only be programmed once, by closing "antifuses". These
retain their programming permanently. The Actel FPGAs are the leading example of
such devices. Atmel FPGAs are currently (July 1997) the only ones in which part
of the array can be reprogrammed while other parts are active.
As of 1994, FPGAs have logic capacity up to 10K to 20K 2-input-NAND-equivalent
gates, up to about 200 I/O pins and can run at clock rates of 50 MHz or more.
FPGA designs must be prepared using CAD software tools, usually provided by the
chip vendor, to do technology mapping, partitioning and placement, routing, and
binary output. The resulting binary can be programmed into a ROM connected to
the FPGA or downloaded to the FPGA from a connected computer.
In addition to ordinary logic applications, FPGAs have enabled the development
of logic emulators. There is also research on using FPGAs as computing devices,
taking direct advantage of their reconfigurability into problem-specific
Usenet newsgroup: comp.arch.fpga.
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