Difference between CPLD and FPGA

The FPGA and CPLD devices were created to obtain the circuit density and speed of ASIC (Application Specific Integrated Circuit) devices, but with a shorter turnaround time for programmable devices. The primary distinction between an FPGA and a CPLD is that an FPGA has more logic resources than a CPLD, which is simpler and has fewer interconnections. Two factors are mostly considered when segregating the FPGA and CPLD. The first is their architecture and how it implements the various logic functions. Second, the specific semiconductor technology utilized in the hardware.

In this article, you will learn about the difference between CPLD and FPGA. But before discussing the differences, you must know about CPLD and FPGA with their advantages and disadvantages.

What is CPLD?

CPLD is an abbreviation for "Complex Programmable Logic Devices". It is an integrated circuit that assists in the execution of digital systems. A CPLD is made up of programmable functional blocks, and each block has macrocells. The CPLD's primary building blocks are macrocells. The I/O of functional blocks is connected through Global Interconnection Matrix (GIM). This interconnection matrix is reconfigurable because changing the contacts between functional blocks is impossible. These functional blocks are equivalent to a set of logic gates.

It is important to consider programming technique, I/P capability, and functional block capabilities when designing CPLDs. In general, CPLDs are nonvolatile and simple to utilize, and they are inexpensive.

CPLDs come in various IC package types and logic families. The supply voltage, standby current, operating current, and power dissipation of CPLDs are also different. Additionally, these are available with different memory capacities and memory support options. Memory is typically measured in bits or megabits, and memory support contains ROM, RAM and dual-port RAM. It also includes FIFO (first-in, first-out) and LIFO (last-in, last-out) memory, and CAM (content addressable memory).

Components of CPLD

There are various components of CPLD. Some main components of CPLD are as follows:

1. Function Block
   In a CPLD, a function block has an AND plane that may accept inputs from I/O blocks, function blocks, or even the same function block's response. After that, the terms are added to the OR array and chosen using a big multiplexer. The output of the MUX may either be moved from the block directly or via a clocked flip-flop. This functional block may also have additional logic, like a selectable exclusive OR, a master reset signal, and the option to program the polarity at several stages.
2. Input/Output blocks
   The Input/Output blocks are utilized to send signals to the CPLD pins at the appropriate voltage and current levels. It allows for the removal of delays, reduction of the device hold time requirements, and the addition of extra resources to the device.
3. Interconnect
   Interconnect of a CPLD is a large matrix of programmable switches that directs the transfer of signals from one portion of the device to another.
4. Programmable Components
   It also utilizes programmable components like PROM, EPROM, EEPROM, and flash EPROM.

Advantages and Disadvantages of CPLD

There are various advantages and disadvantages of CPLD. Some main advantages and disadvantages of CPLD are as follows:

Advantages

1. It is easy to design.
2. It has a low development cost.
3. It helps to reduce the board area.
4. It offers high reliability.

Disadvantages

1. It is a more complicated programmable logic device.

What is FPGA?

FPGA is an abbreviation for "Field Programmable Gate Arrays". It is a semiconductor device composed of a matrix of configurable logic blocks linked together via programmable interconnects. After production, an FPGA may be reprogrammed to meet the requirements. Current FPGAs have approximately 330000 logic blocks with 1100 I/O.

Users may utilize the Hardware Description Language (HDL) to design and configure the circuit. After that, it may execute a simple gate like an AND gate or a complicated system like a multi-core processor. It saves all the configurations in the main memory. As a result, a power failure may delete all these configurations.

Components of FPGA

There are various components of FPGA. Some main components of FPGA are as follows:

1. Programmable logic blocks
   It enables the implementation of logic functions.
2. Programmable Routing
   It enables implementing functions.
3. I/O Blocks
   It is utilized to make chip connections.

Advantages and Disadvantages of FPGA

There are various advantages and disadvantages of FPGA. Some main advantages and disadvantages of FPGA are as follows:

Advantages

1. FPGA ICs are widely accessible and may be quickly programmed using HDL code. As a result, the solution is offered to the market faster.
2. In FPGA design, the software handles routing, placement, and timing. It requires less manual involvement. The design flow removes time-consuming and complicated place and router, floor planning, and timing analyses.
3. FPGAs have the ability to be programmed at the logic level. As a result, it may implement faster and more parallel signal processing. It is challenging for the CPU to execute.
4. Unlike ASIC development, which involves significant NRE (Non-Recurring Expenses) and expensive tools, FPGA development is less expensive due to less expensive tools and no NRE.
5. FPGAs can be programmed at the software level at any time. As a result, the FPGA IC could be reprogrammed or reused unlimited times. FPGAs may also be programmed from a distance.

Disadvantages

1. Power consumption is higher, and programmers have little control over power optimization in FPGA.
2. FPGAs are ideal for prototyping and low-volume production. When the number of FPGAs to be created increases, so does the cost per product also increases.
3. FPGA programming needs familiarity with the VHDL/Verilog programming languages as well as digital system basics. The programming is not as straightforward as that utilized in processor-based gear. Engineers must also learn how to use simulation tools.
4. Once an FPGA is chosen and employed in the design, developers must use the resources present on the FPGA IC, which limits the design size and features. A proper FPGA must be selected from the start to avoid such a problem.

Key differences between the CPLD and FPGA

There are various key differences between CPLD and FPGA. Some of the key differences between CPLD and FPGA are as follows:

1. CPLD is an abbreviation for Complex Programmable Logic Devices. In contrast, FPGA is an abbreviation for Field Programmable Gate Arrays.
2. A CPLD is an integrated circuit that assists in the execution of digital systems. In contrast, an FPGA is an integrated circuit that is mainly created to be customized after manufacturing by a customer or a developer.
3. FPGAs may include up to 100,000 small logic blocks. In contrast, CPLDs may only store a few thousand logic blocks.
4. FPGA is appropriate for complicated apps. In contrast, CPLD is better suited for simpler apps.
5. FPGA has a larger power usage. In contrast, CPLD has lower power consumption.
6. In terms of performance, FPGA provides stable performance that is independent of internal routing. In contrast, CPLD has unpredictable performance that is based on routing.
7. The CPLD is equivalent to the PAL. On the other hand, FPGA is similar to a Gate array.
8. FPGA is a digital logic chip that is based on RAM. In contrast, CPLDs are EEPROM-based.
9. FPGA is classified as fine grain. In contrast, CPLD is coarse grain.
10. CPLD is provided more protection than FPGA because it has nonvolatile memory.
11. Delays in CPLDs are significantly more predictable than in FPGAs.

Head-to-head comparison between CPLD and FPGA

Here, you will learn the head-to-head comparisons between CPLD and FPGA. The main differences between CPLD and FPGA are as follows:

Conclusion

FPGAs offer greater complexity and flexibility and features such as on-chip RAM, clock management, DSP operations, multipliers, etc. On the other hand, CPLD consumes less power than FPGA, and FPGA devices are more likely to be used frequently in designs where changes are applied. In contrast, CPLD devices are used when a simple glue logic is required and when instant-on circuits are needed for the app because FPGA works at a slower speed initially due to the loading of configuration from the external ROM.