Bitstream

November 21, 2023 - Around 2 mins mins to read

What Is Bitstream?

Bitstream is a term used to describe a set of instructions or a program stored in a Field Programmable Gate Array (FPGA) file. It is called FPGA Bitstream because it consists of a sequence of bits.

FPGA Bitstream

The FPGA bitstream file is utilized to configure the pinout and set up the internal logic modules of an FPGA. It is generated using Hardware Description Language (HDL) and can be configured using an FPGA tool.

In the context of FPGA, Bitstream is a digital logic circuit design that configures the device. It can be seen as a sequence of bits that defines the function of the design.

FPGA stands for field-programmable gate array, which is an integrated circuit that can be configured by a customer or designer after manufacturing. This means that the configuration of the integrated circuit can be changed according to the customer’s requirements. The configuration can be done using software or hardware means. Software means take more time to configure, while hardware means take less time but consume more power and programming effort, which is not feasible for large projects. Therefore, hardware configuration is commonly used for FPGAs.

To program an FPGA device, a file in Verilog or VHDL language is required. This file describes how the integrated circuit should behave.

Full vs Partial Bitstreams

A full bitstream is the program that runs on the FPGA and controls all of the I/O pins. It also has RAM and flash memory attached to it. On the other hand, a partial bitstream is a program that runs on the FPGA and is responsible for implementing only part of the design.

Using a partial bitstream implementation in an FPGA is a time-saving strategy as it avoids implementing unused portions of the design. It is also known as partial reconfiguration or partial compilation. The partial bitstream can be written using the parallel interface on the target device or using a host computer.