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'[OT] P.C. Parallel Port Strategy Question'
Does anybody know a strategy for getting around the fact that a
device I am connecting to a P.C. parallel port does not have an ACK or return
data strobe output? The P.C. printer port has an ACK input and a Busy line
and the device I am connecting to the port does have a Busy line, just no
ACK. Once, I had this same problem with an Apple II parallel port but the
situation was a little different. That device had no input buffer so the
Busy line followed each input character. I turned it in to an ACK
line by connecting its output to a one-shot and feeding the one-shot to
the ACK input on the printer port.
I am asking the question to see if anybody knows of a simple
work-around. The cable I am making is the type with crimp-on pins so an
idea of what to do before hand will save some material and time otherwise,
I could just cut and try. If I have to build an ACK generator, then that
will change the whole physical construction of the cable to accommodate
a module with a one-shot and whatever else I need to make the timing right,
possibly another one-shot to slow down the output stream. This device
was made around 1981 or 82 just about the time the IBM P.C. came out so
it isn't even mentioned in the manual.
If I remember corectly I did some work with a device that only used the busy
line (a cash till) the printer was conected through this device and the busy
was flaged when the till opned this stops the flow of char's so if the busy is
aranged to pulse after each char then this should hold the PC until it is
released when it can send the next char.
A nother thaught If a small cap and pull up res are used between strobe and
ack this may slow down the data flow sufficently to opperate your device (cant
remember if pull up or down is correct) the strobe pulses are rather short
just streching this pulse may be enough to enable corect opperation allowing
your device to activate the busy on buffer full.
Just a thaught Steve.....
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