Greg Andrzejewski wrote:
"mdj" <mdj.mdj@gmail.com> wrote in message 1157074498.502604.280610@b28g2000cwb.googlegroups.com">news:1157074498.502604.280610@b28g2000cwb.googlegroups.com...Greg Andrzejewski wrote:Exactly. I/O from the parallel port doesn't require ECP/EPP. On IBM's SPP, 4status lines are used to read a nibble from a device (creatively termed 'nibble mode'). A decent description can be found here http://www.fapo.com/nibble.htm. Using nibble mode allows the SPP tointerface with more than just printers (tape drives, scanners, zip drives,etc).This is the old HP Bitronics mode. In theory the cards Michael mentioned have the means to control such devices, assuming all the control lines are wired.Yeah, that's the thing. I've been looking at pinouts of different Apple II parallel cards and they all seem to be missing one or two control lines present on an SPP. The decision then become whether to try to modify an existing parallel card or (gasp) try to create my own.....
When the original 1977 Apple Parallel Printer card was designed by Woz,
the only signals coming back from the printer that the computer needed
to act on were "busy" and "character strobe" ("I got that character").
Conditions like "paper out", etc., were expected to be dealt with by
the user observing the printer control panel, not by getting a message
from the computer.
The unique way of "reading" the "ready" signal by applying it to
an address input on the card's ROM, causing it to exit an otherwise
endless loop was a very "Woz" trick.
Apple later produced a fully bidirectional Parallel Interface Card
that was provided both with printer firmware and more general drivers.
-michael
New, faster SUDOKU v2.0 solver for Apple II's!
Home page: http://members.aol.com/MJMahon/
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