Morrow Rev.1 Motherboards (MD-1 and MD-2 MicroDecision Computers)

I/O Map
---------------------------------------------------------
Port        Function
----        --------------------------------------
0F5         Motor Check Port

0F6         ROM Enable/Disable (output=enable, input=disable)

0F7         VFO Count Set Port

0F8         Motor and Shift Control

0F9         not assigned

0FA         UPD-765 Status    (Floppy Disk Controller Chip)

0FB         UPD-765 Data      (Floppy Disk Controller Chip)

0FC         1st Serial Port Data

0FD         1st Serial Port Status

0FE         2nd Serial Port Data

0FF         2nd Serial Port Status

Morrow Rev. 2 Motherboards  (MD-3 MicroDecision Computers)
(Kohjinsha and Korean Motherboards, same schematic, different layout ) 

I/O Map Addendum
-------------------------------------------------------------
Port        Function
----        ----------------------------------------
0F0         see below 
0F1         see below
0F2         see next below
0F3         8253 Timer/Counter Used As Baud Rate Generator Ch. 1 and 2

0F4         Centronics Parallel Printer Port: Data Port

0F5         Centronics Parallel Printer Port: Status Port         
            read bit 3 for ACK = 1
            write bit 7 for STB = 0
            read bit 4 for BUSY = 1

All Rev. 1 Ports remain the same except 0F5Hex, not needed for motor check.

-Steve Walz   rstevew@armory.com   http://www.armory.com/~rstevew