VHDL

14

Programmable Logic Devices

CHAPTER OBJECTIVES

• What are PLDs
• Need for PLDs
• Types of PLDs
• Introduction to FPGAs and CPLDs
• Differences between FPGAs and CPLDs
• Implementing digital design using FPGAs/CPLDs

14.1 INTRODUCTION

Programmable logic devices (PLD) refers to integrated circuits which can be programmed to implement any digital system. It gives an immediate realization of the logic circuit and can be reprogrammed allowing the same IC to be used again, and PLD can be upgraded in the field without any need for removing it from the chipboard. PLDs were introduced in 1970s with the idea to design a single purpose chip which can be programmed to meet particular hardware requirements. Earlier systems used SSI and MSI ICs as TTL 7400 series ...