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From: tom@ramona.Cary.NC.US (Tom Salzmann)
Newsgroups: comp.sys.ibm.pc.programmer
Subject: Programming a COM port, raising DTR
Message-ID: <819@ramona.Cary.NC.US>
Date: 11 Apr 90 01:48:38 GMT
Sender: news@ramona.Cary.NC.US
Lines: 15

I am looking for code examples (MASM or C) of how to properly raise
DTR on a COM port.  I have an application which dials the modem
after raising DTR.  The problem is that this application works fine
on most systems, but on a few systems it simply won't raise DTR all
the time.  Here is a segment of code I use to do it:

        MOV     DX, port address + offset for modem control register
        MOV     AL,0BH
        OUT     DX,AL

Should something more robust be done to properly raise DTR?   Please
reply to me directly and I'll gladly summarize here once I become an
expert on the subject. :-)
--
Tom Salzmann <tom@ramona.Cary.NC.US>