The 6808 has a simple motorola style bus with no multiplexing. The board is therefore fairly minimal. U3A-U3C turn the Motorola E clock and RW signals into RC2014 (Z80 style) \RD and \WR signals. A 74HC688 (U2) matches addresses of the form $FExx and generates IORQ for those and MREQ otherwise.

Jumpers allow the E clock and RW line to be put onto pins 38/39 (user pins) of the bus, the same as the other 65xx and 68xx cards so that they can be used with 68xx/65xx style peripheral cards like the 6522 VIA.

The input clock should run at four times the frequency of the processor. For the 6808 that means 4MHz max, for the 68A08, 6MHz for the 68B08 8MHz. It is thus possible to run a 68B08 with the standard 7.37MHz RC2014 clock, but the other parts require a slower clock.