Documation - Apple I/O

From: John Lawson <>
Date: Thu Dec 26 16:22:00 2002

  Just to take the "opto / no opto" discussion public.. in respect of
connecting the Documation TTL outputs to the TTL inputs of an Apple VIA
card in an Apple ][ ...

  I respectfully beg to disagree with my Learned Friend Dr. Duell. As I
privately wrote to Sellam, I am afraid of (and have been badly bitten by)
directly interfacing dissimilar machines, and then encountering
poorly-designed power supplies that 'hunt' and attempt to regulate each
other over the logic lines, with occasionally spectacular results.

  Wiring up a couple of octal or hex optoisolators should take a two hours
max, and then no worries, Moit!

  I am just trying to err on the side of caution. Were it me, with my
resources and equipment, I'd just measure between the devices to make sure
no VooDoo was lying in wait, then go ahead and splice the cables. In
Sellam's case, he does not have rooms full of sophisticated test gear, and
so I thought isolating the signals would serve to protect the machines,
especially the card reader I/O circuits.

  Your Milage May Vary, as they say.


Received on Thu Dec 26 2002 - 16:22:00 GMT

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