Memotech I/O Port Assignments

As illustrated by the diagram above, the Z80 is capable of addressing up to 64k of I/O ports, but commonly, only 256 I/O ports are used, addressed through the lower 8 bits of the address bus. All of the MTX and expansion I/O ports are addressed by 8-bits, i.e., up to 256 I/O ports are supported by the MTX hardware.

I/O Port assignments for the Memotech MTX computer are listed in the Operator's Manual and ports for the FDX are listed in the FDX Technical Manual, both of which are available on my manuals page. In addition to the I/O ports used by the original Memotech hardware, a number of ports have been allocated to various modern day enhancements such as REMEMORizer, CFX, MFX, etc.

Andy Key has hosted a comprehensive list of MTX I/O ports on the hardware page on his Memotech site for a number of years, however, it has not been updated for some time and omits a number of ports used by more recent hardware developments. Bill Brendling has edited a copy of Andy's original table to capture all of the known I/O ports used by original Memotech hardware and more recent developments. The modified table is available here.