Re: Handshake cable

[dempson@atlantis.actrix.gen.nz (David Empson)]

In article <3ngh92$v7@asia.lm.com>,
Matt Portune <mportune@telerama.lm.com> wrote:
> John L. Graham (fl332@cleveland.Freenet.Edu) wrote:
> > Ack! I can't remember off the top of my head, but 7 <-> 8 might be
> > the GPi <-> DCD line, if so I don't think it's required unless your
> > computer is serving as the host.
> 
> It says in the spectrum manual, as well as my other texts, that pin 7<->8 
> is required for hardware handshaking.

The manual is wrong.  DCD is not required for hardware handshaking
(which is just CTS/RTS).  Nor is DTR.

There are six basic types of Mac/IIgs-to-modem cables:

Handshake     DCD?        Description
In   Out      

DSR  DTR      no          "standard" modem cable without DCD
DSR  DTR      yes         "standard" modem cable with DCD
CTS  RTS      no          "hardware handshake" without DCD
CTS  RTS      yes         "hardware handshake" with DCD
CTS  RTS/DTR  no          "hardware handshake" without DCD, with DTR
CTS  RTS/DTR  yes         "hardware handshake" with DCD and DTR

The last one in the list is what Spectrum wants - a cable with
everything connected.

The DTR connection in a hardware handshake cable is of no practical
use when used with hardware handshaking.  It is only useful if
hardware handshaking is disabled and the modem is told to drop carrier
when DTR is lowered.
-- 
David Empson
dempson@actrix.gen.nz
Snail mail: P.O. Box 27-103, Wellington, New Zealand