Digital programming is a very important course in digital circuits. FPGA and CPLD are two important programming tools. This article brings you to know the connection and difference between fpga and cpld.
FPGA (Field-Programmable Gate Array), which is a field-programmable gate array, is a product further developed on the basis of programmable devices such as PAL, GAL, and CPLD. It emerged as a semi-custom circuit in the field of application specific integrated circuits (ASIC), which not only solves the shortcomings of the custom circuit, but also overcomes the shortcomings of the limited number of original programmable device gates.
CPLD (Complex Programmable Logic Device) complex programmable logic device, which is a device developed from PAL and GAL devices, is relatively large in scale and complex in structure, and belongs to the scope of large-scale integrated circuits. It is a digital integrated circuit that users construct their own logic functions according to their needs. The basic design method is to use the integrated development software platform, use the schematic diagram, hardware description language and other methods to generate the corresponding target file, and transfer the code to the target chip through the download cable ("in-system" programming) to realize the designed digital system. .
Although FPGAs and CPLDs are programmable ASIC devices, they have many features in common, but due to differences in the structure of CPLDs and FPGAs, they have their own characteristics:
1. FPGA has more flexibility than CPLD in programming. CPLD is programmed by modifying the logic function with fixed interconnect circuit. FPGA is mainly programmed by changing the wiring of internal wiring; FP GA can be programmed under logic gate. The CPLD is programmed under the logic block.
2, CPLD is more convenient than FPGA. CPLD programming uses E2PROM or FASTFLASH technology, no need for external memory chip, simple to use. FPGA programming information needs to be stored in external memory, the use method is complicated.
3, CPLD speed is faster than FPGA, and has greater time predictability. This is because FPGA is gate-level programming, and distributed interconnection between CLB, while CPLD is logic block-level programming, and its logic block The interconnection between the two is lumped.
4. In programming mode, CPLD is mainly based on E2PROM or FLASH memory programming, the number of programming can reach 10,000 times, the advantage is that the programming information is not lost when the system is powered off. CPLD can be divided into programming on the programmer and in the system. There are two types of programming. Most of the FPGA is based on SRAM programming, and the programming information is lost when the system is powered off. Each time the power is turned on, the programming data needs to be rewritten into the SRAM from outside the device. The advantage is that it can be programmed any number of times. Quick programming at work for dynamic configuration at the board and system level.
5, CPLD confidentiality is good, FPGA confidentiality is poor.
6. Under normal circumstances, the power consumption of CPLD is larger than that of FPGA, and the higher the integration, the more obvious.
7, FPGA integration is higher than CPLD, with more complex wiring structure and logic implementation.
8. CPLD is more suitable for completing various algorithms and combinational logic. FP GA is more suitable for completing sequential logic. In other words, FPGA is more suitable for the structure of triggers, and CPLD is more suitable for structures with limited triggers and rich product terms. .
9. The continuous wiring structure of the CPLD determines that its timing delay is uniform and predictable, and the segmented routing structure of the FPGA determines the unpredictability of its delay.
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