•Complex PLDs (CPLDs) consist
of multiple PAL-like blocks on a
single chip
•FPGAs have a much larger number of individual logic blocks than CPLDs, and a
large distributed interconnection structure
–each logic block is much simpler than a PLD
CPLD: small number of large, complex logic blocks
FPGA: large number of small, simple logic blocks
•“Field programmable” means that the devices are configured by a designer
rather than the device manufacturer
•Simplest type of logic block is a lookup table (LUT)
–implemented here using multiplexers and one-bit storage cells (0/1)
•Inputs x1 and x2 drive select inputs on multiplexers
•Any 2-input logic function can be built by programming LUT with appropriate bits
•Easily extended to 3-inputs, 4-inputs, …
Hope this helps