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From: russotto@eng.umd.edu (Matthew T. Russotto)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Carrier Detect
Message-ID: <1991Feb22.151625.26340@eng.umd.edu>
Date: 22 Feb 91 15:16:25 GMT
References: <12468@helios.TAMU.EDU>
Sender: news@eng.umd.edu (C-News)
Organization: College of Engineering, Maryversity of Uniland, College Park
Lines: 19

In article <12468@helios.TAMU.EDU> wwg2101@venus.tamu.edu writes:
>Could someone please tell me how to implement a carrier detect routine for
>use with the modem port? What I want is a boolean function returning true if
>the modem is currently detecting a carrier signal, and I can't for the life 
>of me figure out how to read the CD line from the modem. I am working in 
>pascal on an  SE, but I undertstand C, so example code in C or Pascal would 
>be fine.

Most cables for the Mac do not support the carrier detect line-- they either
support DTR/DSR or CTS/RTS.  On some modems, DSR and CD are equivalent, so
you can read the status of CTS to see if you have a carrier.  On
others, you can make a custom cable and connect CD (pin 8 on the DCE) to
pin 7 on the Mac.  In either case, reading the status of these lines
is going to require some assembly language, and a look at the manual for
the serial chip, unless the Comm Toolbox has added this ability.

--
Matthew T. Russotto	russotto@eng.umd.edu	russotto@wam.umd.edu
     .sig under construction, like the rest of this campus.