The schematic for the MP-09A shows something wierd: both the baud-rate generator chip (14411) and the upper DAT RAM (74LS189) drive the same output buffers for the same four SS-50 lines; their outputs are hard-wired together. And on the schematic, those SS-50 lines are labelled S1/300 baud, S2/4800 baud, S3/1200 baud, and S4/2400 baud. (I've probably listed the wrong baud rates here, but you get the idea). The idea is that any board would have either a baud-rate generator or an upper DAT RAM, but not both. So the same CPU board could be used in systems with a 64K address space and baud-rate signals avaialable to the SS-50 cards, or in those with a one megabyte address space and no baud rates. Examination of MP-09B boards shows that they have places for both chips, although only one of them is actually there on any one board.
The MP-09B could be the CPU board in either a 6809 or an S/09 system. Mine, in an S/09, is rev. A, but has pull-up resistors soldered onto some of the traces from the CPU in what looks like a repair job. So there was probably a rev. B board.
There are eight jumper blocks on this board as well as a DIP switch with four switches, as listed below. The settings in my working system(1) are indicated by an asterisk. Of course, this doesn't guarantee that they are the right settings for anyone else.