[comp.sys.ibm.pc.misc] Using MS int86 to access modem

peter.dorfman@office.wang.com (06/27/91)

I am trying to use the Microsoft C int86 call to interrupt 20 (14H) in
order to access the modem on a Hyundai AT clone. The modem is an Everex
Hayes compatible. DOS = 3.2. I initialize the serial port for the modem
(using int86) then send a series of command characters to the modem (int86).
But the modem does not seem to respond.  And worse, after the routine
completes the system typically hangs soon afterward and needs to be rebooted.

The communications programs on my system work fine, so I know that the
hardware in alright.  Can anybody tell me what I'm doing wrong?  What
is the proper sequence of operations? Thanks in advance for any
assistance.