Path: utzoo!attcan!uunet!lll-winken!lll-lcc!ames!ncar!gatech!udel!rochester!pt.cs.cmu.edu!b.gp.cs.cmu.edu!Ralf.Brown@B.GP.CS.CMU.EDU From: Ralf.Brown@B.GP.CS.CMU.EDU Newsgroups: comp.os.minix Subject: Serial port speeds (was Re: AN HISTORIC MOMENT!) Summary: sure you can go faster than 9600 Message-ID: <22de01d6@ralf> Date: 15 Jul 88 13:00:06 GMT Sender: netnews@pt.cs.cmu.edu Lines: 20 In-Reply-To: <4200004@hpihoah.HP.COM> In article <4200004@hpihoah.HP.COM>, bruce@hpihoah.HP.COM (Bruce LaVigne) writes: }actually stuff into the chip are divisors of an externally input clock. With }the clock that IBM used, if you go above 9600 you start using non-integer }divisors. What this means is that since you can really only use integer }numbers into the chip as a divisor, you don't get 19200 but something kindof }close. If the other side can handle it, fine, but IBM doesn't support it. That is not correct. The divisor for 9600 is 12, so the divisor for 19200 is 6 and for 38400 it is 3. As a matter of fact, it is the 110 baud that is off by a small fraction of a percent, whereas 300/600/1200/2400/etc are all exact (assuming that the clock is exact). However, from what I have heard, early 8250's had problems sync'ing with the incoming signal at >19200. I believe that the various 115k transfer programs use two stop bits to help the chip recognize the incoming data. -- UUCP: {ucbvax,harvard}!cs.cmu.edu!ralf -=-=-=- Voice: (412) 268-3053 (school) ARPA: ralf@cs.cmu.edu BIT: ralf%cs.cmu.edu@CMUCCVMA FIDO: Ralf Brown 1:129/31 Disclaimer? I |Ducharm's Axiom: If you view your problem closely enough claimed something?| you will recognize yourself as part of the problem.