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Newsgroups: comp.unix.bsd.freebsd.misc,comp.mail.uucp Path: euryale.cc.adfa.oz.au!newshost.anu.edu.au!newshost.telstra.net!act.news.telstra.net!psgrain!usenet.eel.ufl.edu!news.mathworks.com!uunet!in2.uu.net!news.nkn.net!rowdy.lonestar.org!nemesis!uhclem From: uhclem@nemesis.lonestar.org (Frank Durda IV) Subject: Re: Taylor-UUCP not running with 16550 SIO (UMC Custom Chip) X-Newsreader: Tin 1.1 PL5 Organization: The Big Blue Box Message-ID: <DnEzEn.2IA@nemesis.lonestar.org> References: <4gruu6$uhq@godzilla.zeta.org.au> Date: Tue, 27 Feb 1996 03:08:46 GMT Lines: 30 Xref: euryale.cc.adfa.oz.au comp.unix.bsd.freebsd.misc:14667 comp.mail.uucp:15893 Bruce Evans (bde@zeta.org.au) wrote: [5]Yes, mine loses sync if the fifo enable bit is toggled or the speed is [5]set while part of a character has arrived. The UART apparently syncs If you will look at the NS16550 documentation, it states that changing the state of the FIFO bit will cause a loss of data in the TX and RX shift registers and in the TX and RX FIFOs. You never change these bits after the chip is initialized or while data is moving through the device if you want the data to be sent/received intact. NS even recommends toggling the FIFO bit as a way to flush the contents of the FIFOs to abort the transmission of data you have already given to the UART but now don't want to send. How this bit is treated also differs in the various clones, mainly because Microsoft turns it on and leaves it on, and Microsoft products are the main compatibility test the clone-16550 makers use. The same thing goes for changing parity, word size, stop bits, baud rate and other parameters while data is in the UART. What you get is not defined. Information on the NS16550 registers can also be found in the -current FreeBSD handbook (see uart.sgml). Frank Durda IV <uhclem@nemesis.lonestar.org>|"The Knights who say "LETNi" or uhclem%nemesis@rwsystr.nkn.net | demand... A SEGMENT REGISTER!!!" |"A what?" or ...letni!rwsys!nemesis!uhclem |"LETNi! LETNi! LETNi!" - 1983