A flash microcontroller has a Static Random-Access-Memory (SRAM) buffer that stores several blocks of boot code read from a flash memory. The SRAM buffer also operates as a cache of flash data after booting is complete. Cache read and write hits use the SRAM cache rather than flash memory, while old cache lines and read misses access the flash memory. Both the external host and the microcontroller are booted from boot code buffered in the SRAM buffer. A boot-loader state machine reads the flash ID and programs flash parameter registers with timing parameters for the flash memory. The flash microcontroller uses a differential interface to the external host, with a differential transceiver and a differential serial interface. Frame, packet, and encoded clock processing is also performed by the serial interface.