This document describes a design for a modification which allows a CPC6128 to read both single and high density discs.
THIS modification has not been tested so may not work!
The CPC must have a SED9420C Data-Seperator.
I/O port &FA7F has been chosen. &FA7E is the recommended I/O port for floppy disc motor. Due to the partial decoding of the I/O ports &FA7F will also access floppy disc motor in unmodified CPC6128. It is known that some copyprotected software uses &FA7F instead of &FA7E to access floppy disc motor, so this modification may cause problems with that software. Maybe a re-design to cope with this is required?
Modification to CPC6128 possible. Modification to CPC+ requires more work.
|1||selects clock to FDC.|
0 = 4Mhz, 1 = 8Mhz
0 = MFM, 1=FM.
(MFM for double density and high density)