🚀 go-pugleaf

In article <1992Sep7.003326.1873@proforma.com> jgg@proforma.com (J. G. Gregory)  
writes:
> I trying to set up a NeXT for dialin on ttyda, via a Hayes 2400 modem.  This  
is  
> for UUCP, but that is irrelevant, I believe.
> 
> Two years ago, when I tried to do this, I ran into the problem whereby when  
the  
> getty was turned "on" for ttyda, it would not "block waiting for DCD to be  
> asserted", and would spit the login: prompt out immediately upon being reset.   
> This was on a 68030, and I proved that EVEN WITH NOTHING CONNECTED, this  
> behavior would occur.  i.e., it was not the cable or the modem.  Despite my  
> hopes, it was not solved with the 68040 upgrade or any of the software  
> releases.
> 
> Since that time, a message appeared on the net regarding this problem, and I  
> snarfed off, knowing I would come by this path again.  Here is the relevant  
> part of that post:
> 
> > open(2) does indeed block as advertised, but only if you have a
> > device connected to the port which ties the DCD pin LOW (ground
> > state).  By default, the port will float DCD HIGH (asserted or
> > "true")... To simulate this, connect the DCD pin to ground via
> > a dropping resistor (say 1k ohm).  voila! open blocks. Disconnect
> > the resistor and voila! the open goes through. Check what your
> > attached device does. You may be surprised.
> 
> Now, how do I get everything to work as advertised?  Can the modem be set to  
> hold the DCD low (it is set per the docs, &C1)?  Will the resistor trick work  
> other than for just a test?  While I have real problems understanding why a  
> dropping resistor is necessary on a NeXT with a Hayes modem (spent extra to  
get  
> modem NeXT mentioned), I can put it on if I have to.  But there has got to be  
a  
> better way.  Does any know what it is?
> 
As I read it, the advice above is demonstrating how to prove DCD control does  
work.  It is not meant to be used in an actual installation.  What he's saying  
is that with nothing connected to the DCD line, it will float in the direction  
that does not block the open.  You need to check you modem's DCD line control,  
most modems default to always asserting that line true.  Read through the AT  
command set, or on older modems, check the dip switches!

> I would also like to hear from people who are successfully using a NeXT with  
> both dialin and dialout working (without editing /etc/ttys in between).
> 
I'm using yrrid's ttydsp on an '030 at 57.6kbs with a v.32bis/v.42bis modem  
with no problems. ;-)

> Thanks in advance.
> --J Gregory

Jim