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Friday, January 10, 2020

VLSI & Microelectronics | FPGA Architecture ,importance,advantage


FPGA Architecture 

Introduction
The full form of FPGA is “Field Programmable Gate Array”. It contains ten thousand to more than a million logic gates with programmable interconnection. Programmable interconnections are available for users or designers to perform given functions easily. A typical model FPGA chip is shown in the given figure. There are I/O blocks, which are designed and numbered according to function. For each module of logic level composition, there are CLB’s (Configurable Logic Blocks).
CLB performs the logic operation given to the module. The inter connection between CLB and I/O blocks are made with the help of horizontal routing channels, vertical routing channels and PSM (Programmable Multiplexers).
The number of CLB it contains only decides the complexity of FPGA. The functionality of CLB’s and PSM are designed by VHDL or any other hardware descriptive language. After programming, CLB and PSM are placed on chip and connected with each other with routing channels.
The general FPGA architecture consists of three types of modules. They are I/O blocks or Pads, Switch Matrix/ Interconnection Wires and Configurable logic blocks (CLB). The basic FPGA architecture has two dimensional arrays of logic blocks with a means for a user to arrange the interconnection between the logic blocks. The functions of an FPGA architecture module are discussed below:
• CLB (Configurable Logic Block) includes digital logic, inputs, outputs. It implements the user logic.
• Interconnects provide direction between the logic blocks to implement the user logic.
• Depending on the logic, switch matrix provides switching between interconnects.
• I/O Pads used for the outside world to communicate with different applications.
Advantages
It requires very small time; starting from design process to functional chip.
No physical manufacturing steps are involved in it.
The only disadvantage is, it is costly than other styles.

Importance of FPGA
FPGA hold promise of delivering even in harsh conditions. The cyclone devices from Altera work well in temperature ranges of -40 degrees to 85 degrees. Another factor that promotes their long term use is the long term availability. ASIC manufacturers do not agree on availability of 5 or at maximum 10 years, where as FPGAs have nearly unlimited availability even if device migrates to next generation.
These find use in microprocessor systems like the PowerPC405 embedded cores, in Digital Signal Processing as embedded multipliers and in I/O Processing like Digitally controlled Impedance. It is always better to be sure of the design and its performance by testing it on FPGA’s before going in for ASIC circuits. These are employed in Defense systems and medical imaging. The possibility of evolvable hardware was revealed while implementing speech recognition  on an FPGA using genetic algorithm. FPGAs being parallel processing devices find use in applications like brute force attacks used in breaking cryptographic algorithms, in convolution and FFT computations.


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