View Full Version : "Clock Plus Card" software or docs

November 21st, 2006, 06:48 PM
Hi, I'm a newbie here.

I have an old "Clock Plus Card" for an XT class machine.
I have no software nor docs for it. It has a battery, a
couple small IC's and a Mitsubishi M5L8255AP-5 chip which looks
like it does most of the work. Seems to be set to use
ports 0x20c to 0x20f. Anyone have one, or seen software for
it? I did download the Mitsubishi spec sheet which give some
clues, but I really rather not attempt to write my own access
program! I have not found anything about this on the net.


November 21st, 2006, 07:03 PM
I know it's not what you were looking for but interesting none the less.


I have read about 8255 for years and years in the PC world. I never was too clear what it was used for.

November 21st, 2006, 09:31 PM
Ah, here's better info.


I would have lost a bet that the 8255 was involved with the 18.2 per second IRQ0 interrupt. I was almost sure that it was but I see that is covered by the much more logical 8284A generator.