Re: Imagewriter vs modem cable

[bellm@mail.med.upenn.edu (Marcus G Bell)]

Nathan Mates (nathan@visi.com) wrote:
: In article <E243z0.84G@murdoch.acc.Virginia.EDU>,
: James  Burtoft <jb6z@faraday.clas.Virginia.EDU> wrote:
: >Both are serial cables, right?  Does one have more "wires"
: >going out (like handshaking vs. non-handshaking modem cables?)
: >If so, which has more?
: >Or are they both interchangeable with each other?

:    A printer cable is a modem cable with a null-modem built in. Very
: much non-interchangeable unless you use an even number of printer
: cables and null modems.

OK, aprpopos of this, I bought a null modem 25 pin - 25-pin cable, and
a Mac modem mini8 DIN - 25 pin handshaking cable. Everything I need to
hook my new GS to my PC, I thought.

I can send data PC -> GS just fine when the mini8 is plugged into the
GS modem port, but GS -> PC only if the mini8 is plugged into the
printer port and "printer echo" is on (half duplex on the modem port
configuration).  I have my control panel settings set correctly in
terms of slots, etc. I even turned hardware and software flow control
off, but this problem persists.  The same sort of thing happens when I
substute a real modem at the end of the modem cable. I watch the
lights on the modem, and I see the handshaking and data lights flicker
at excectly the same rate when the GS sends data through the printer
port, as if the handshaking and data lines were shorted together. The
GS only receives data from the modem through the modem port, but
cannot send it to the modem through the modem port.

I think the Mac modem cable is wired improperly on its handshaking
pins. I'm ready to take the cable back and butcher an Imagewriter II
mini8-mini8  cable to make my own null modem cable. At least I'd be
able to wire CTS, RTS, DTR, DSR, CD, etc. properly so that the PC
would think the GS was a modem, and vice versa.

What say you GuruS?

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Marcus. ( bellm@mail.med.upenn.edu )