Programmable Logic Technology

Chapter 3 is an introduction to programmable logic technology. The capabilities and internal architectures of the most popular CPLDs and FPGAs are described. These include the Cyclone FPGA used on the FPGA board, and the Xilinx 4000 family FPGAs.

Older traditional off-the-shelf integrated circuit chips, such as SSI and MSI TTL, performed a fixed operation defined by the device manufacturer. A user must connect a number of different chip types to build even a simple logic circuit with this older technology. A large number of chips will also be required as each chip contains only a few basic logic gates. Application specific integrated circuits (ASICs), complex programmable logic devices (CPLDs), and field programmable gate arrays (FPGAs) are integrated circuits whose internal functional operation is defined by the user. ASICs require a final customized manufacturing step for the user-defined function. A CPLD or FPGA requires user programming to perform the desired operation.