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Newsgroups: comp.unix.bsd Path: sserve!manuel.anu.edu.au!munnari.oz.au!spool.mu.edu!sdd.hp.com!zaphod.mps.ohio-state.edu!usc!sol.ctr.columbia.edu!eff!news.byu.edu!ux1!fcom.cc.utah.edu!cs.weber.edu!terry From: terry@cs.weber.edu (A Wizard of Earth C) Subject: Re: [386bsd] 16550 and rtscts patch Message-ID: <1992Dec14.171834.7500@fcom.cc.utah.edu> Sender: news@fcom.cc.utah.edu Organization: Weber State University (Ogden, UT) References: <Bz25Io.L40@ucunix.san.uc.edu> Date: Mon, 14 Dec 92 17:18:34 GMT Lines: 46 In article <Bz25Io.L40@ucunix.san.uc.edu> pmartin@eniac.san.uc.edu (Paul Martin) writes: > >I applied the rtscts flow control patch to the com driver that was >posted here sometime back. Now I cannot send anything to the modem. The >modem does not receive the characters, and the command: >echo ats0=1 > /dev/com2 >seems to hang until I shut off the modem. This worked before the patch. >I am using 16550's. By the way, the mouse on com1 still works fine. > >Any Ideas? I haven't had a chance to look at the patch yet (I did save it off); I suspect that the problem is that the inverse level is being looked at (ie: only with the RTS deasserted can you send). The other possibility is that the CTS assert/RTS require order is munged, and your modem needs your serial prot to assert before it can assert, and your serial port needs the same (ie: starvation deadlock). In general, it can be said that *nobody* does CTS/RTS as "expected", and unless you have a Bell 103 dataset, you can't expect it to work quite right without a lot of tweaking. The other possibility is that *many* modems will not assert RTS until they have carrier; this is fine for dial-in to a UNIX box, but dial out expects to be able to dialog with the modem without DCD *or* RTS present. If you are using a "calling unit" version of the device, this problem should be taken care of for you on dial out (although I can't vouch for whether or not the patch only applies to "calling unit" devices AFTER DCD has been asserted. I assume since you can "shut off" your modem that it's external. If you have a breakout box, you may want to watch the signal levels to/from the modem to confirm your problem. Terry Lambert terry@icarus.weber.edu terry_lambert@novell.com --- Any opinions in this posting are my own and not those of my present or previous employers. -- ------------------------------------------------------------------------------- "I have an 8 user poetic license" - me Get the 386bsd FAQ from agate.berkeley.edu:/pub/386BSD/386bsd-0.1/unofficial -------------------------------------------------------------------------------