DS3100/dc0 support for modem control

[Olof Backing]

ttl at sti.fi (Timo Lehtinen) writes:

>The dc(4) man page (in ULTRIX V3.1D) says that the serial line controller
>on DECstation 3100 and 2100 only provide partial modem control. Could
>anyone enlighten me as to what functionality specifically is missing ?

>I'm writing a program which needs to sense whether Carrier Detect is on
>and can't figure out how to do it. For instance

>	ioctl(fd, TIOCWONLINE); /* wait for carrier */

>never blocks regardless of whether I have a cable on the port or not.

>Is it me or the dc0 ?

>Any help much appreciated,

>From what I've heard from the DECpeople here in Sweden, the serialport
on a DEC3100 (and I guess DEC2100) will only support the following:

1 - frame ground
2 - TxD
3 - RxD
6 - fuzzy comb. of DCD & DSR
7 - signal ground
8 - see pin 6
20 - outgoing DTR

But thats only valid for one of the serialports. Cant remember which
one at the moment, but do a 'file /dev/tty0[01]' and you'll see.

WHOAMI: Olof Backing                                  EMAIL:
WHERE:  Swedish Institute of Computer Science (SICS)  obg at sics.se
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