IBM 6094-020 Lighted Program Function Keys

Michael B. Brutman mbbrutman-cctalk at
Mon Jul 30 23:56:33 CDT 2007

dwight elvey wrote:
> Hi
> First try removing the Maxim chip. It may be shorted. Next,
> send a copy of the code you are using to control and what
> frequncy the processor is running at. If the crystal isn't 12 MHz
> ( as I recall ) the baud rate may be differnt.
> Dwight

I've checked the output from the MCS-51 by putting a probe on the leg 
and noticed the same thing.  I think the Maxim is dutifully raising the 
voltage to 10VDC from 5VDC, as it should.

I don't have control over the code - it's probably burned into this 
variant of the MCS-51.  Even if I have the bps rate wrong, I should 
still some garbage flowing across serial interface.


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