The SPI Interface Project
Majid Pakdel · 2025
This chapter focuses on interfacing an external SPI flash memory with the Arty A7 FPGA development board. It begins by introducing the external QSPI flash chip, detailing its purpose of storing FPGA configuration files to enable nonvolatile operation. The chapter explains the SPI protocol, including MOSI, MISO, SCK, and CS signals, and demonstrates communication between a master (FPGA) and slave (flash memory) device. Different SPI modes, including standard, dual, and quad SPI, are discussed, emphasizing speed and pin requirements. The chapter outlines the design strategy using the MicroBlaze MCS soft processor and a custom VHDL SPI interface to facilitate read/write operations. Additionally, it covers the memory organization of the external flash and step-by-step instructions for generating and programming memory configuration files (.mcs) onto the flash, ensuring safe FPGA configuration and reliable data storage.