The Multitech MPF-1Plus, the successor of the MPF-1(B)

When BASIC became a requirement in the 1980's for educational computers, the MPF-1 became too limited. It has a Tiny-BASIC, but with only six 7-segment displays and a hex-keyboard, usage is not very user- friendly.

The MPF-1Plus or MPF-1P, was Multitech's anwser to this problem. With a 20 character display of 14-segment characters (virtual line-length is 40 characters) and a 'full' ASCII keyboard, the MPF-1P resembels a normal computer.

Front view

MPF-1Plus with startup banner on display.

The computer came incomplete, but in overall good condition. The power connector, speaker and the monitor ROM were added. The cassette port sockets will come later.

One minor repair:

  • The display brightness fluctuated with the number of digits in on-state, which was also reflected in the anode voltage. The standard -30 volt was reduced to about -18 volt with the startup banner on display. After making sure this wasn't caused by old, dried-out electrolytic capacitors (33uF/35V), the driver transistor, an old TO-18 2N2222A was replaced with a newer TO-92 of the same type.
IOM-MPF-1P

IOM-MPF-1P board for the MPF-1P with PIO, CTC, 8251 installed.

The IOM-MPF-1P board contains the brings back the extra's that were part of the 1B, but were absent from the 1P, a Z80 PIO, a Z80 CTC, an experiment area and adds some more: a 8251 PCI (programmable communication interface) with RS232c connector, 6 kByte RAM and 2 kByte ROM.

The contents of the ROM is a bit underwhelming, as it are mere simple demo's for the interface chips:

B000h
PIO demonstration using the three LEDs as traffic light.
B100h & B700h
CTC demonstration as a clock. Two versions.
B300h
PCI & CTC demonstration of reading the DIP-switches for the baud-rate, and sending a message over the RS232c interface. If a CRT (TVB-MPF-1P) board is present in the configuration, a message is send there too.

Startup commands:

CONTROL-A
Enter two pass assembler
CONTROL-B
Enter BASIC language
CONTROL-C
Re-enter BASIC
CONTROL-D
Enter disassembler
CONTROL-E
Enter and initialize the text editor
CONTROL-L
Enter the one pass assembler
CONTROL-P
Toggle printer output on/off
CONTROL-Q
Re-enter the monitor
CONTROL-R
Re-enter the text editor

Monitor commands (incomplete set)

B
Examine breakpoint address.
Baaaa
Set new breakpoint for address aaaa.
BC
Clear breakpoint.
Daaaa/
Change the top of the range to be shifted to aaaa. Same as Iaaaa?
Daaaa
Shift data from aaaa+1 to the top of the range to aaaa. A 00 is added at the top.
Daaaa bbbb
shift data from bbbb+1 to aaaa 00's are added at the top.
Faaaa bbbb cc
Fill memory from address aaaa to bbbb with value cc.
Gaaaa
Execute program code starting at address aaaa.
Iaaaa dd [ee [ff [gg [hh [jj .... ]]]]]
Insert starting at address aaaa values dd, ee, ff, gg, .... The I command shifts existing values at aaaa and up upwards in memory.
Iaaaa/
Change the top of the range to be shifted to aaaa.
Jaaaa bbbb
Calculate the relative jump address from aaaa to bbbb. The range is from -128 to +127.
Lnnnnn
Read program with name nnnnn from tape.
Maaaa
Display data at address aaaa to aaaa+3. Use ↑ and ↓ keys to browse memory.
Maaaa[:dd [ee [ff [gg [hh [jj .... ]]]]]]
Insert starting at aaa the data dd, ee, ff, gg, hh. One value is mandatory, more is optional. Maximum?
Maaaa/bbbb cccc
Copy data in range aaaa - bbbb to cccc
Maaaa.bbbb
Dump memory from address aaaa to bbbb. Useful with MPF-PRT or MPF-TVB.
Rrr
Examine register contents. Use ↑ and ↓ to browse registers. Use ' for alternate registers.
S
Execute next instruction in Single step mode. The ↑ and ↓ keys can be used to inspect and change register contents.
Saaaa
Start single step execution at address aaaa.
Waaaa bbbb nnnnn
Write data from address aaaa to bbbb to tape with program name nnnnn.

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Last update: 2022-11-12