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From: jerry@gumby.Altos.COM (Jerry Gardner)
Newsgroups: comp.os.msdos.programmer,alt.msdos.programmer
Subject: Re: Serial port control?
Keywords: DTR, reset state?
Message-ID: <4790@gumby.Altos.COM>
Date: 8 Apr 91 22:18:29 GMT
References: <1991Apr8.044312.29004@hubcap.clemson.edu>
Reply-To: jerry@altos.COM (Jerry Gardner)
Followup-To: comp.os.msdos.programmer
Distribution: na
Organization: Altos Computer Systems, San Jose, CA
Lines: 22

In article <1991Apr8.044312.29004@hubcap.clemson.edu> dawill@hubcap.clemson.edu (david williams) writes:
>
>   I've just recently aquired my *own* PC, rather than fooling around
>with the computers the school so nicely lets me use.  Here's the 
>question:  How do I set the DTR line inactive after some terminal
>program has finished with the serial port?  


To deassert DTR, write a 0 to bit zero of the serial port's Modem Control
register.  This register is at I/O port address 0x3fc for COM1 and at
0x2fc for COM2.  Writing a zero to the register will deassert all of the
modem control lines.  An example in C follows:


	outp(0x3fc, 0);		/* turn off all modem control lines */


-- 
Jerry Gardner, NJ6A					Altos Computer Systems
UUCP: {sun|pyramid|sco|amdahl|uunet}!altos!jerry	2641 Orchard Parkway
Internet: jerry@altos.com				San Jose, CA  95134
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