Re: [neonixie-l] ZX81 Nixie Clock

Michel van der Meij Mon, 22 Apr 2013 14:54:46 -0700

Thanks Jim, that's a great looking IBM you got there!

No cheating on the ZX81 clock though. I posted the schematics to a dedicated facebook page:

https://www.facebook.com/Zx81NixieClock

It is really not much more than an address decoder and some latches :-).

The hours and minutes are written to the latches with a simple instruction OUT (C), A with the hours in B and minutes in A (both in BCD of course).
Every time the latches are written, the state of the colon lights is inverted. So writing the latches twice per second keeps the colon flashing. The HV power down is active when $0C is written to the minute register. You would need to write this twice, I did that because I didn't want the HV circuit to turn on in the case power was restored after a power failure.

Michel

on Apr 22, 2013, J Forbes <jforbnos...@selectric.org> wrote:

Looks good! Old computers are fun, they still do what they used to do when they cost a lot, but now they're cheap and we can discuss them on the internet....

I cheated on my vintage computer nixie clock....I used one of David's old kits, and just stuck it into an early IBM case (which also houses our media computer, so it gets to be front center in the living room)

http://selectric.org/ibmpc/atxpc33.jpg

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Re: [neonixie-l] ZX81 Nixie Clock

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