Path: utzoo!attcan!uunet!cs.utexas.edu!hellgate.utah.edu!fcom.cc.utah.edu!cc.utah.edu!cc.usu.edu!jrd
From: JRD@cc.usu.edu (Joe Doupnik)
Newsgroups: comp.sys.ibm.pc.hardware
Subject: Re: Modem works (but in the dark)
Message-ID: <41240@cc.usu.edu>
Date: 26 Oct 90 19:12:12 GMT
Lines: 14


	The most common reason a modem will appear to "work" (meaning it can
respond to commands from the PC) and still not yield information to the PC
is the IRQ line for the modem is not responding. And the reasons for that
are missetting of jumpers to other than 4 or 3, other things sitting on
the same IRQ and active at the same time, other. What this means is the
port address is ok so the modem gets commands from the PC but the modem's
responses generate no usable interrupts to dump characters into the comms
program.
	Still one more case is the modem is not even close to being like
the standard 8250 UART. MS-DOS Kermit responds by using the Bios and the
Bios may not provide any responses until DSR and CTS are asserted by the
modem.
	Joe D.