Many people, especially students and beginners, get confused when it comes to choosing between FPGA and CPLD as both of them are well-known digital logic chips. However, their internal architecture differs in various parameters.
FPGA vs CPLD
The main difference between FPGA and CPLD is that FPGA (Field Programmable Gate Array) has a complex architecture, which is considered fine-grain, whereas CPLD (Complex Programming Logic Design) has a simpler architecture, which is considered a coarse grain.
FPGA is a programming logic chip with a complex and fine grain architecture. It is based on RAM. It is volatile, which means that if the power is disconnected, it will lead to a loss of data. It is comparatively more suitable for complex applications. It also consumes more power in comparison. It is also more expensive.
On the other hand, CPLD is designed with the help of EEPROM, and it has a simple, coarse grain architecture. It is more suitable for simpler applications. It is non-volatile, which means that if the power is disconnected, it won’t lose any data. It tends to consume less power when compared to FPGA.
Comparison Table Between FPGA and CPLD
| Parameters of Comparison | FPGA | CPLD |
| Full-Form | Field Programmable Gate Array | Complex Programming Logic Design |
| Architecture | Fine-grain | Coarse grain |
| Density | Medium to high | Low to medium |
| Power consumption | High | Medium |
| Cost | Expensive | Cheap |
| Based on | RAM | EEPROM |
| Volatility | It might lose the data if power if disconnected. | Disconnection of power won’t cause any loss of data. |
| Ratio of flip flops | More | Less |
| Applications | Better for complex applications | Better for simpler applications |
| Performance | A predictable performance that is independent of internal placement and routing. | Performance is dependent on the routing. |
What is FPGA?
FGPA stands for Field-Programmable Gate Array, which is a programmable logic chip. It can be programmed to do different types of digital functions. It is an integrated circuit that is specially designed to be configured by customers or designers after the manufacturing process.
It provides a massive amount of logic resources and storage elements that can help in the creation of complex systems. Its architecture is considered fine-grained. This lets the chips have a higher logic capacity.
It is made up of up to 100,000 tiny logic blocks and also consists of a combination of logic, flip-flops, and memory. It is more on the expensive end but can be more affordable if you are buying it per gate.
It is RAM-based, which means it requires some special procedures. To program a device, you must first describe the ‘logic function’ using a computer. This results in the creation of a binary file that can be downloaded into the FPGA.
FPGAs use an external ROM to load configuration data and set up the fabric before it starts functioning. This means that there will be a time delay after you start it and before it starts working.
It is not that easy to predict any delays in this programming. It also consumes more power. It is also comparatively less secure. Its performance is dependent on the routing that has been implemented for a particular application.
FPGAs tend to use SRAM-based configuration storage. It means that it is volatile. The data stored in the memory may be lost if the power is disconnected.
What is CPLD?
CPLD stands for Complex Programmable Logic Device. It is an integrated circuit that can be used to implement digital systems. It is designed with the help of electrically erasable programmable read-only memory, more commonly known as EEPROM.
Its architecture is less complex, which makes it more suitable for simple logic applications. It only has a few logic blocks, going up to 100. They are coarse-grain types of devices.
They are non-volatile, which means that their data won’t be lost if the power is disconnected. They are cheaper than FPGAs and offer a faster input to output duration. This is due to their simple architecture.
CPLDs start as soon as you power them up. The delays are predictable and time analysis is easier to do. This is because they are simpler, and the number of interconnects is less. They also have a lower power consumption.
They are considered more secure because of their design storage which is built-in within the non-volatile memory. Its performance is predictable and independent of internal placing and routing. It is suitable for low to medium-density designs.
It can only be reprogrammed a limited number of times. It provides minimum logic resources. They are more suitable in small gate count designs.
Main Differences Between FPGA and CPLD
- FPGA stands for Field Programmable Gate Array, and CPLD stands for Complex Programming Logic Design.
- FPGA is an integrated circuit that is designed specially to be configured by customers or designers after the manufacturing process, whereas CPLD is an integrated circuit that can be used to implement digital systems.
- FPGA is considered a fine grain, and CPLD is coarse grain.
- FPGA has higher power consumption, and CPLD has a lower power consumption comparatively.
- FPGA is based on RAM, whereas CPLD is based on EEPROM.
- FPGA is more expensive, and CPLD is cheaper.
- FPGA is suitable for complex applications. On the other hand, CPLD is better for simpler applications.
- In terms of performances, FPGA has a predictable performance that is independent of internal routing, whereas CPLD has a performance that depends on the routing.
Conclusion
Both FPGA and CPLD are great, popular digital logic chips. They were developed to achieve the circuit density and speed, which can be similar to ASIC but has a shorter turnaround time. FPGA provides extensive logic resources, whereas CPLD is simple and contains a smaller number of interconnections.
FPGA is more suitable for complex applications as it has a fine grain and complex architecture, whereas CPLD is more suitable for simpler applications as it has a simple and coarse grain architecture.
References
- https://ieeexplore.ieee.org/abstract/document/500200
- https://books.google.co.in/books?hl=en&lr=&id=vggmNXdzayYC&oi=fnd&pg=PP1&dq=fpga+and+cpld&ots=s7HjirG-ea&sig=15OMJOILY2a0Z0–fBnq551-KPk&redir_esc=y#v=onepage&q=fpga%20and%20cpld&f=false