Serial & Memory Card for the Microprofessor MPF-IB

The Serial & Memory Card is part of an effort to make a Z80 system, in this case the MPF-IB, as easy to program as an Arduino. It contains a serial port, with a monitor in ROM and a configurable amount of memory.

The board populated with DART, monitor ROM and RAM with its configuration logic

The serial port is provided by a Z80 DART, of which the monitor uses only the B channel. It is interfaced with a three wire connector (Rx, Tx, GND) intended to be used with a serial-to USB interface to a computer.

Serial subsystem

The DART is default configured to use I/O-ports E0-E3h. This can be changed by jumpers to another set of ports in the E4h-EFh range.

The Baud rate is configurable between 19200 and 75 bd.

The A channel is currently not used by the monitor. It is equipped with a full set of handshake lines and a TTL-RS232c converter. The signals are provided to a 9-pin sub-DE and a 10-pin header. This header is commonly found on (vintage) mainboards featuring serial ports.

Memory subsystem

The whole Z80 CPU addressing range is covered by two 32k Byte static RAM chips. The read and write signals can be set independently for each 4 k Byte segment.

The RAMs can be replaced by non-volatile memory, assuming a compatible pinout.

Not all of the memory can be used, as ranges 0000h-0FFFh and 1800h-1FFFh are used by the MPF-I monitor. The extra ROM socket with the serial monitor is mapped to F000h-FFFFh.


As of version 0.3, the monitor uses somewhat less than 2 kByte and has the following set of commands:

ZMC80 Monitor Command List
? - view command list
C - clear screen
D - print 100h bytes from specified location
E - edit bytes in memory
F - fill memory range with value
G - jump to memory value
M - copy bytes in memory
P - print port scan (00-FF)
R - monitor reset (jump to 0000h, MPF-monitor)
+ - print next block of memory (from last displayed block)
- - print previous block of memory (from last displayed block)


The board is not for sale, but the KiCAD design files and monitor code (assembly and code) are free for download. The V1.2 is build, tested and working, with one minor error (on the ROM socket, U7, pin 18 should be connected to pin 20). As long as no other errors are found or new features needed, a new version is not likely.


These apply to the v1.2 version.


Last updated: 2022-03-01