FPGA or CPLD, and which one to use? It is a common question often asked by people who are first getting into hardware design. There will never be a definite answer on which one is better since it depends on the person’s needs.
What is FPGA?
FPGA stands for Field Programmable Gate Array. An FPGA is a device that can store and program digital circuits during runtime.
The basic concept of an FPGA is that it implements all the logic functions in its logic gates. This means that they are not hard-coded into the FPGA by a designer. However, we can change them by just writing a program to the proprietary hardware description language (HDL).
It is a programmable FPGA with the following physical characteristics. Many logic elements and programmable interconnects.
Look-Up-Tables (LUT) blocks allow the FPGA to have as many possible combinations of product terms.
It has RAM blocks that we can use to store the results generated by the logic gates when we are programming them. We can also reconfigure the gates in FPGAs within a shorter period compared to CPLDs. This is because we can clock the logic gates in FPGA faster than a CPLD.
It uses its OS to control the individual logic blocks written in it. The power consumption of an FPGA is less than a CPLD because of the smaller die size. This is because it does not have any transistors except the logic gates.
What is CPLD?
A CPLD is an integrated circuit (IC) consisting of logic cells, memory cells, and I/O cells. We connect them on a silicon chip by traditional wire bond bonds or flip-chip bonding. Unlike an FPGA, it is not programmable. We hardwire the full functionality of the logic block into the IC’s design, and we cannot change them even if we reprogram the IC.
CPLDs are suitable for implementing small designs since small ICs consume less power than the FPGA. They are also easy to use since there is no need to use a separate hardware description language (HDL) to configure the logic gates.
The main difference between CPLDs and FPGAs is that CPLDs do not change their configuration during runtime. It means they have a fixed functionality in time, while we can expand or change FPGAs at runtime.
The basic concept of a CPLD is that we implement all the logic functions in its logic gates. Manufacturers hardwire the configuration into the IC’s design, and they cannot change them even if we reprogram the IC.
CPLDs are suitable for implementing small designs since small ICs consume less power than FPGAs. They are also easy to use because there is no need to use a separate hardware description language (HDL) to configure the logic gates.