I recreated the schematics for the controller by tracing the connections by hand. Click on the schematic for a larger version. You can download it here as an sPlan file.
(Last updated August 9, 2023)Programming the controller is very similar to the descriptions in the FD1771 datasheet. In addition to the four ports described in the datasheet (addressed as extended IO-ports 80-83), the floppy controller uses extended IO-port 84 to read the interrupt status, or to select one of four disk drives. Drive 0 and 1 are on the first unit, side A and B; drive 2 and 3 are on the second unit, side A and B. Getting the floppies to work is my next goal, as soon as the memory is working reliably. If you have any further information on this card, please let me know.
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