What is FPGA?

Fpga (Field Programmable Gate Array), that is, field programmable gate array, is the product of further development on the basis of programmable devices such as PAL, GAL and CPLD. As a semi-custom circuit in the field of application specific integrated circuit (ASIC), it not only solves the shortcomings of custom circuits, but also overcomes the shortcomings of limited gates of the original programmable devices.

Working principle of FPGA

FPGA adopts the concept of logic cell array (LCA), including configurable logic block (CLB), input-output block (IOB) and interconnection. Field programmable gate array (FPGA) is a programmable device. Compared with traditional logic circuits and gate arrays (such as PAL, GAL and CPLD devices), FPGA has different structures. FPGA uses small lookup table (16× 1RAM) to realize combinational logic. Each lookup table is connected to the input of a D flip-flop, which drives other logic circuits or drives I/O, thus forming a basic logic unit module that can realize both combinational logic functions and sequential logic functions. The logic of FPGA is realized by loading programming data into internal static storage unit. The value stored in the storage unit determines the logical function of the logic unit and the connection mode between modules or between modules and I/O, and finally determines the function that FPGA can realize. FPGA allows unlimited programming.

Basic characteristics of FPGA

1) Using FPGA to design ASIC circuit (application specific integrated circuit), users can get a shared chip without production.

2)FPGA can be used as a pilot sample for other fully customized or semi-customized ASIC circuits.

3) There are abundant flip-flops and I/O pins in 3)FPGA.

4)FPGA is one of the devices with the shortest design cycle, the lowest development cost and the least risk in ASIC circuits.

5) FPGA adopts high-speed CMOS process, which has low power consumption and is compatible with CMOS and TTL levels.

It can be said that FPGA chip is one of the best choices for small batch system to improve system integration and reliability.

The working state of FPGA is set by the program stored in the on-chip ram, so it is necessary to program the on-chip RAM when working. Users can adopt different programming methods according to different configuration modes. At power-on, the FPGA chip reads the data in the EPROM into the on-chip programming RAM, and after the configuration is completed, the FPGA enters the working state. After power failure, the FPGA reverts to blank, the internal logic relationship disappears, and the FPGA can be reused. The programming of FPGA does not need a special FPGA programmer, just use a general EPROM and PROM programmer. When the function of FPGA needs to be modified, just replace an EPROM. In this way, the same FPGA and different programming data can produce different circuit functions. Therefore, the use of FPGA is very flexible.