Multitech Micro-Professor MPF-1

The MPF-1B can still be bought from Flite Electronics

Sam Bergmans' Legendary MPF-1 pages including hexperiments.

PDF documentation and ROM dumps for the Multitech MPF-1 computer

The Bugbook Historical Microcomputer Museum

Some day I will research the different versions out there. Hans Otten has pictures of two different versions and neither is the one I have. My one matches the MPF-1B at the Centre for Computer History.

The Old Computer has ROM dumps.

MPF-EPB is a board with four memory devices and an EPROM programmer that connects to the Z80 CPU BUS connector.

Other expansion devices.

Mike Hawkins' PureMP / PureMPF MPF-1 emulator.

My MPF-1

This is my MPF-1, serial number 4229.

One RAM is a Hitachi HM6116, the other a Mitsubushi M58725. Both are 2k x 8.

I replaced the 6116 with a 2716 with the CTC interrupt driven clock program from the Experiment Manual, relocated to $2000. Built it into a shadow box for display.

The second pic shows what happened when I took a photograph with the flash on... the EPROM puts out garbage for a few cycles and the CPU reboots. Guess I should put stickers on the EPROMs.

Also, you need to use nylon spacers (or washers, I suppose), the PCB has a power track on the one side and a ground track on the other, right by the mounting holes.

Experiment Manual CTC Clock Example

I am flabbergasted at how kak this code is. It's simple, catch an interrupt, increment a counter, do nothing all day.

So they take the 1789800 Hz system clock, run it through the divide-by-256 prescaler, divide it by another 32 in the CTC, and then count to 218 in the code for a total division of 1785856 to give an error of 2.2 ms per second. So this thing runs slow by almost 8 seconds an hour. Enough power to land a man on the moon, and 8 seconds error each hour.


OK, to get the absolute best accuracy you need a 16-bit counter for the last stage, and maybe that was too advanced. But even if they had used 30 in the CTC and 233 in the software the error would have decreased by an order of magnitude. Some spreadsheeting shows that the best 8-bit software counter value is 184 with the CTC counting to 38, for an error if 85 us per second, almost 26 times better than the example. The best possible result is with a 16-bit software counter running to 6991 with the CTC just providing the divide-by-256 prescaler -- 58 us per second.

There might be a better solution using the divide-by-16 prescaler but I have not investigated that.

So change location 1823H to B8H and location 1809H to 26H and enjoy a much-improved clock.

At this stage I need to set the time manually, but it would be nice to add a real-time clock, so...

--- work-in-progress line---

Dallas DS1216

The Dallas DS1216 SmartWatch is a socket that piggybacks a RAM chip. It then provides battery backup to the RAM, as well as a Real Time Clock, using the DS1315 Phantom Time Chip on a little PCB with two batteries and a crystal.

There are/were various versions (B-H) catering for 16 kilobit to 4 megabit devices. I happen to have a C version in my junkbox -- this is intended for use with 6264 (8k x 8) to 62256 (64k x 8) 28 pin devices. But the Micro Professor uses 6116 (2k x 8) RAMs.

The DS1216 is powered from pin 28 (this is the one connection that doesn't connect from the socket to the RAM. Power goes from the socket to the DS1315 and from there to the RAM). Plugging it into a 24 pin socket won't work.

Of course, I've had this SmartWatch since before the Berlin Wall came down. The built-in batteries are flat flat.

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