An IBM I/O Selectric interface using TTL and a 2708 EPROM

steven at steven at
Tue Dec 22 22:43:27 CST 2015

Back in the late 70s early 80s one of Dad's work colleagues came up with this circuit for interfacing
an IBM I/O Selectric to a microcomputer. We had one, which we planned to use with our Fairchild/Mostek
F8 development board, but it never got done - my brother and I wanted a computer with a screen, not a
printer! So we spent our pocket money (and Dad's too) on an S-100 kit system, but that's another story.
Recently I found the only remains of our I/O writer, the platen. Sadly I think it must have been junked,
the platen being kept to roll out photographic prints in Dad's darkroom.

I just finished scanning, cleaning up the degradation and turning the circuit into a PDF. These days an
Arduino or RasPi would be a simpler and more flexible way to go, but I hope you find it interesting
looking at how it was done with TTL and discrete components.

The circuit was designed by (I believe) Neil Taylor, possibly with the help of Derek Williamson, both
brilliant IBM Australia CE's. I know my dad always spoke very highly of them.

It's an 8-page PDF at


Steve Malikoff.

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