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 ...

[Raendra] posted a guide for using one of these chips, it’s a Microchip MCP23008 chip that uses the I2C protocol for communications. You are probably already familiar with using shift registers ...