The Serial Peripheral Interface (SPI) is a full-duplex, synchronous, serial data link that is standard across many microprocessors, microcontrollers, and peripherals. It enables communication between microprocessors and peripherals and/or inter-processor communication. The SPI system is flexible enough to interface directly with numerous commercially available peripherals. A SPI Master design has been implemented in a CoolRunner XPLA3 CPLD. The CoolRunner SPI Master design can be used to provide a SPI controller to those microcontrollers or microprocessors that do not contain a SPI interface. A high-level block diagram is shown in Figure 1. The microcontroller (μC) interface chosen in this SPI Master implementation is based on the popular 8051 microcontroller bus cycles, but can easily be modified to other microcontroller interfaces. For more information on the 8051 microcontroller interface, please refer to XAPP349, CoolRunner CPLD 8051 Microcontroller Interface.