A compact register set gives the SPIFI peripheral a considerable amount of intelligence while keeping it simple to use. It takes just eight registers to control the SPIFI function, interface with the external SPI memory, store and retrieve data, and monitor operation. Since the built-in ROM API handles setup, programming, and erasure, handling the external SPI memory in an application is only a matter of a few API calls. As a result, the SPIFI peripheral is simple to configure and easy to support in the application. The API also automatically detects which Quad SPI Flash device is connected by reading its JEDEC number and configuring SPIFI to optimize performance of the external serial Flash. The external memory responds to commands sent by the microcontroller software and to commands automatically sent by the SPIFI peripheral when its software reads the serial Flash region of the memory map. Commands are divided into fields called op-code, address, intermediate, and data. The address, intermediate, and data fields are optional depending on the op-code. Data fields are further divided into input and output data fields depending on the op-code. All commands to the external SPI memory can be handled by calls to the ROM API. The SPIFI ROM API driver lets the contents of the external SPI memory be accessed using simple load commands, so the application code remains simple and easy to write.