Can the DZ look at DSR instead of CXR?

[Dave Sherman]

We have a PDP-11/23 running v7, and an educational source license.
Some of our DZV11 (== Qbus version of DZ11, same dz.c code) lines
are hooked up to a PAD (packet assembler/disassembler) which is
connected to the Datapac network.

The DZ looks at CXR (carrier detect) to determine whether the DCE
it's talking to is on-line. In our configuration, because the PAD is
physically connected, CXR is always high. When a call is active, the
PAD sets DSR high. Knowing whether a call is active is important,
since if the Datapac user disconnects without logging off, a
hangup signal must go to his processes.

I suppose I can have RS-232 connectors made up which will map
DSR from the PAD into CXR for the DZ, and ignore CXR coming from
the PAD.  But I'm wondering if there's another way. Can the DZ
driver be told to look at DSR instead of CXR? (I've glanced at
the dz.c source and really don't know where to look.)

Thanks for any help on this.

Dave Sherman
The Law Society of Upper Canada
Toronto
(416) 947-3466

ARPA: allegra!utcsrgv!dave at BERKELEY
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