From: misdcc@otago.ac.nz (Denis Gordon)
Newsgroups: comp.sys.prime
Subject: Re: Async cables for modems
Date: 13 Nov 92 09:28:24 +1300
Organization: Dunedin City Council, Dunedin, NZ

In article <9211101441.AA00525@usenet.rpi.edu>, JCROSS_PUBMAIL@prime.mhsl.uab.edu writes:
> 
> We are starting to experience heavy modem use.  One problem is that
> when a user disconnects from the modem (i.e. hangs up the telephone
> line) the async line and whatever was being run is left dangling.
> 
> I'm using the "-DISLOG" option of the "SET_ASYNC" command but this
> doesn't seem to be having any effect.  Apparently the async
> communications cables used to connect the modems to the 9 pin async
> connection on the Prime doesn't allow the Prime to monitor the
> carrier signal.  I tried using a  standard Prime supplied async
> communications cable but it doesn't work.
> 
> I really need to be able to have a user forced logged out if he is
> dialed in by modem and hangs up the telephone line.  Can someone
> please send me the diagram for the proper cable and advice as to what
> options to use when setting up the async communications lines to be
> used by the modems.

We have a similar situation with a large number of users sharing a small
number of ICS ports via a (now obsolete) network. We finally got it working
by fine tuning the following CONFIG directives:

dtrdrp                         /* Controls dropping of DTR when users logout
dislog yes                     /* Logs out user when line is disconnected   
amltim 2 0 4540                /* Free lines not logged in after 4 mins     

We found the description of the AMLTIM directive in the manual to especially
confusing and spent considerable time & effort with a breakout box between
ICS port & network. The following explanation of the arguments is from
LIST_CONFIG:
    Directive           Argument            Current    Cold-start   Default     
      name            description            value       value       value      
+-----------------------------------------------------------------------------+ 
| AMLTIM        | ticks (seconds/10)     | 2        | 2          | 2          | 
| AMLTIM        | disctime (seconds/10)  | 0        | 0          | 3410       | 
| AMLTIM        | gracetime (seconds/10) | 4540     | 4540       | 0          | 
+-----------------------------------------------------------------------------+ 

DTR is dropped on all ICS ports that do not have a logged in user every 240
seconds (the arguments are in octal). This gives users between 4 and 8 minutes
to log in before the comms connection is dropped.

DTRDRP causes DTR to be dropped when the user logs out and DISLOG logs out
the user if CD drops (comms connection lost).

The cables we are using are simple cross-over cables (our network has DTE
ports) so I guess the fololwing straight thru cable should work.

      Modem       PRIME
       DB25        DB9

      TD  2 ----- 2  TD
      RD  3 ----- 3  RD
               +- 4 RTS      
               +- 5 CTS
      SG  7 ----- 7  SG
      CD  8 ----- 8  CD
     DTR 20 ----- 9 DTR


Hope this helps
Denis.

-- 
Denis Gordon       <misdcc@otago.ac.nz>
Network Controller
Dunedin City Council                      DUNEDIN. It's all right here!
Dunedin, New Zealand                                        ~~~~~