FPGA Architecture | Configurable Logic Block ( CLB ) | Part-1/2 | VLSI | Lec-75

Summary

This video provides an in-depth explanation of the basic architecture of an FPGA (Field Programmable Gate Array). It covers key components such as IO pads for external communication, Configurable Logic Blocks (CLBs) which are the heart of the FPGA, and their internal structure including Lookup Tables (LUTs), D flip-flops, and multiplexers. The video also discusses how interconnects and the switch matrix facilitate data transfer between these blocks. By understanding these building blocks, users can gain insights into how FPGAs are programmed and reprogrammed to implement various digital logic functions.

Takeaways

• 😀 FPGAs (Field Programmable Gate Arrays) are programmable arrays where logical elements are interconnected, and the internal program can be reprogrammed at any time.
• 😀 FPGAs allow users to design and change logic circuits on-demand, offering flexibility in designing different logic functions.
• 😀 I/O pads (or I/O blocks) are used to connect the FPGA to external devices for data transfer in any direction (top, bottom, left, right).
• 😀 I/O blocks surround the FPGA, enabling easy connection with external devices without the need for long wiring.
• 😀 The internal architecture of an FPGA includes Configurable Logic Blocks (CLBs), interconnects, and a switch matrix.
• 😀 CLBs are the heart of the FPGA, consisting of logic elements like Lookup Tables (LUTs), D Flip-Flops, and multiplexers to implement logic functions.
• 😀 LUTs in CLBs can implement logic functions with a maximum of four inputs; for more inputs, multiple CLBs are used.
• 😀 D Flip-Flops in CLBs provide delayed outputs based on clock pulses, and multiplexers select between the direct output or the delayed version.
• 😀 The interconnection wires in the FPGA connect the CLBs to transfer data and allow communication between them.
• 😀 The switch matrix is responsible for interconnecting the horizontal and vertical lines of the FPGA, ensuring that data can be transferred between various parts of the FPGA.
• 😀 The FPGA's modular structure, with I/O pads, CLBs, and interconnects, makes it a versatile tool for custom logic implementation and efficient data processing.

Q & A

What does FPGA stand for?

FPGA stands for Field Programmable Gate Array, which is a programmable logic array that can be reconfigured at any time to implement different logic functions.

What is the main advantage of FPGA?

The main advantage of FPGA is its reprogrammability. You can modify the internal program and design logic circuits, allowing for flexibility in implementation.

What are IO pads in FPGA used for?

IO pads (or IO blocks) are used to connect the FPGA to external devices, enabling the transfer of data to and from the FPGA. They surround the FPGA board to make it easier to interface with external systems.

What are the key components of an FPGA architecture?

The key components of FPGA architecture include IO pads (or IO blocks), configurable logic blocks (CLBs), interconnects, and the switch matrix.

What is a Configurable Logic Block (CLB) and why is it called the 'heart' of FPGA?

A CLB is a fundamental building block of FPGA. It performs the logic operations and consists of a lookup table (LUT), a D flip flop, and a multiplexer. It is called the 'heart' of FPGA because all logic operations are carried out within it.

What is the role of the Lookup Table (LUT) in a CLB?

The LUT in a CLB implements the logic function based on the corresponding truth table. It can handle logic functions with up to 4 inputs.

How does the D Flip Flop function in a CLB?

The D flip flop in a CLB is used to provide a delayed version of the output from the LUT. It stores data temporarily and ensures the logic function is executed with a delay based on the clock pulse.

What is the purpose of the multiplexer (MUX) in a CLB?

The multiplexer in a CLB selects either the direct output of the LUT or the delayed output from the D flip flop. It allows flexibility in choosing between different logic outcomes.

How does the interconnection system work in FPGA?

The interconnection system, comprising interconnects and the switch matrix, allows CLBs to be connected to each other and communicate. The switch matrix routes data between CLBs, enabling flexible connections across the FPGA.

Why are IO pads located around the FPGA board?

IO pads are placed around the FPGA to provide easy access for connecting the FPGA to external devices in any direction (top, bottom, left, right). This setup simplifies the connection process and reduces the need for long wiring.