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Everything you want to know about Xilinx CPLDs!

  What is a CPLD?
  Why use a CPLD?
  Why Xilinx CPLDs?
  Choosing a Xilinx CPLD
  Designing with CPLDs
  XC9500XV
  XC9500XL
  XC9500
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  Mature XPLA Families

 

What is a CPLD?

In order to understand CPLDs (Complex Programmable Logic Device), it is important to understand SPLDs. An SPLD (Simple Programmable Logic Device) is a lot of gates with interconnects that can be programmed to form desired logic functions. There are two basic types of SPLDs: the PLA and the PAL. The PLA has both a programmable AND array and a programmable OR array and looks like this:

PLA Diagram
Signetics - Cline - 1975

The PAL has a programmable AND array with a fixed OR array and looks like this:


PAL Diagram
MMI - Birkner - 1978

CPLDs are simply a joining of 2 or more SPLDs on a single IC using an interconnect, making them look like this:

CPLD Block Diagram

All CPLDs utilize macrocells in their device architecture. These macrocells allow for combinatorial or sequential logic, and also have the added flexibility for true or complement, along with varied feedback paths.

 

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