This I/O board will have a 65C22 providing two 8-bit I/O ports. I have included an I2C Interface that uses two pins on Port B. It will also have my 65SPI chip providing an SPI interface using the 65SIB format. I have also included an SBC-3 compatible SPI interface that will allow one SBC-3 device to be connected to the SS6 input.
Here's a picture of the conceptual layout:
This is the schematic:
I'll add more once I've finished the design.