The PIC uses I2C to communicate with the configuration EEPROM, so a little snooping on the bus went a long way. Dumping things out led to finding the frequency settings. By part six of the post ...

Put on “Nevermind” and dig into a nicely done retro project. The emulator is basically a PIC 16C54 microcontroller and some memory, with some buffers for input and output. On one side ...