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What is a Field Programmable Gate Array (FPGA)?
A field programmable gate array (FPGA) is a type of digital integrated circuit (IC) that can be programmed after manufacturing, or reprogrammed after deployment, to perform different types of logical tasks.
FPGAs are useful for applications whose functional requirements may change over time or in situations where the same integrated circuit may need to be repurposed for an entirely different task.
Techopedia Explains the Field Programmable Gate Array Meaning
In the context of field programmable gate array definitions, a “gate” is an electronic circuit building block that can perform a specific logical operation on one or more binary inputs and produce a single output.
A gate array is a type of integrated circuit that has a predefined grid of interconnected transistors, logic gates, and electronic components.
Gate arrays are usually fabricated in a fixed pattern by the hardware manufacturer. In a field programmable gate array, however, the gate array’s configuration is not fully specified during the manufacturing process. This allows it to be customized for specific applications.
How FPGA Works
Field programmable gate arrays consist of programmable logic blocks and a hierarchy of reconfigurable interconnects that allow the blocks to be wired together.
FPGAs also include memory elements for storing information. The memory elements consist of simple flip-flops that hold single bits and memory blocks that can hold more data. One of the memory blocks will store settings for how the IC’s programmable logic blocks and interconnects are configured.
When the integrated circuit is powered up, the settings are compiled into a bitstream. The FPGA interprets the bitstream and reconfigures its internal circuits accordingly.
Some FPGAs have non-volatile memory that can store configuration settings permanently, but many FPGAs use volatile memory and the configuration settings will be lost when the hardware is powered down. FPGAs that use volatile memory have to be re-configured on each power-up with a configuration bitstream loaded from an external non-volatile memory source.
It’s worth noting that FPGA configurations need to be programmed with a hardware description language (HDL) like VHDL or Verilog. This type of specialized programming is usually done by a hardware engineer, embedded systems engineer, research scientist, or industry-specific field service engineer.
Why are FPGAs Needed?
FPGAs address a unique set of IC needs that application-specific integrated circuits (ASPICs) and software-reliant microcontrollers can’t address.
ASICs are expensive, and their development can be complex and time-consuming. Usually, their cost can only be justified in use cases where the volume of production is high enough to amortize the initial investment over many units.
Microcontrollers, which can be thought of as the brain for a system on a chip (SoC), execute instructions one at a time. This limits their performance for tasks that benefit from massive parallelism, where FPGAs excel.
FPGA vs. ASIC, Microcontroller
Field programmable gate arrays, ASICs, and microcontrollers serve different purposes and have distinct characteristics. The choice between an FPGA, ASIC, and microcontroller depends largely on the specific needs of the project.
Why and When to Use FGPA?
FPGAs strike a balance between cost, performance, and time to deployment. Here are four compelling reasons to choose FPGAs for specific use cases:
- One of the most significant advantages of FPGAs is their ability to be reprogrammed and reconfigured after manufacturing. This means you can update the device to change its functionality or fix a bug without needing to redesign or replace the hardware.
- FPGAs facilitate rapid prototyping and testing. Their reprogrammability can significantly accelerate the development process and reduce the time to market.
- FPGAs excel in handling complex algorithms and computations that can be parallelized.
- FPGAs are ideal for industries and market segments where technology or standards are rapidly evolving. Their flexibility and adaptability can significantly extend a product’s lifespan.
Types of FGPA
There are four basic types of field programmable gate arrays. They are categorized by their internal architecture and the methods used to program their configuration settings.
These FPGAs use volatile static RAM (SRAM) to store their configuration settings and external memory to load the configuration bitstream on power-up. SRAM-based FPGAs are arguably the most popular type of FPGA because they are relatively inexpensive and can be reprogrammed fairly easily.
Antifuse FPGAs use non-volatile memory and are one-time programmable (OTP). Their field programming creates permanent electrical connections within the FPGA, which can’t be changed later on. Antifuse FPGAs are known for being secure, but they lack the reconfigurability of SRAM-based FPGAs.
These FPGAs use non-volatile flash memory to store configuration settings and the configuration bitstream. They can be reprogrammed more than once. They provide a middle ground between SRAM-based and antifuse FPGAs.
EEPROM-based FPGAs use electrically erasable programmable read-only memory to store configuration settings and the configuration bitstream. This type of FPGA has largely been replaced by flash-based FPGAs.
FPGA Use Cases
FPGA versatility makes them suitable for a wide range of applications. Common use cases include:
FGPA Pros and Cons
FPGAs excel when flexibility and adaptability are crucial. They are particularly valuable for prototyping, lower-volume applications with evolving requirements, or tasks that require high-performance parallel processing.
However, their cost, power consumption, and development complexity need to be carefully considered when compared to alternative solutions.
The suitability of FPGAs depends heavily on the specific application and other technologies it’s being compared against. When there are significant trade-offs between flexibility, performance, and cost, FPGAs often provide a middle ground.
| Feature | Pros | Cons |
| Flexibility | Can be reprogrammed for different functions | Limited compared to pure software solutions |
| Performance | High parallel processing for specific tasks | Can be slower than ASICs for optimized workloads |
| Development | Faster prototyping than ASICs | Requires specialized HDL knowledge |
| Cost | Cheaper than ASICs for low-medium volume | More expensive than general-purpose CPUs/microcontrollers |
| Power | Customization can improve efficiency | Generally more power-hungry than ASICs |
| Security | Harder to remotely exploit, customizable | Still vulnerable to physical and side-channel attacks |
The Bottom Line
FPGAs bridge the gap between general-purpose processors and custom ASICs. However, FPGAs require specialized skills to program and manage. The decision to use FPGAs should be based on a thorough analysis of project requirements and balance the need for flexibility against the cost, complexity, and power efficiency of the solution.
FAQs
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References
- VHDL Tutorial – Introduction to VHDL for beginners (Nandland)
- Verilog.com (Verilog)
- Amortization in accounting 101 (Tax.thomsonreuters)
