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Xref: sserve comp.os.linux.development:18513 comp.os.linux.misc:28637 comp.os.386bsd.questions:14181 comp.os.386bsd.misc:3926 sci.electronics:83078 Newsgroups: comp.os.linux.development,comp.os.linux.misc,comp.os.386bsd.questions,comp.os.386bsd.misc,sci.electronics Path: sserve!newshost.anu.edu.au!harbinger.cc.monash.edu.au!bunyip.cc.uq.oz.au!munnari.oz.au!spool.mu.edu!howland.reston.ans.net!EU.net!sun4nl!rnzll3!sys3.pe1chl!rob From: rob@pe1chl.ampr.org (Rob Janssen) Subject: Re: 16550 detection Reply-To: pe1chl@rabo.nl Organization: PE1CHL Message-ID: <CyntLn.HD@pe1chl.ampr.org> References: <CMETZ.94Oct30051603@itchy.inner.net> <SRA.94Oct30162124@rurha-pente.epilogue.com> <CMETZ.94Oct30192816@itchy.inner.net> <CyIzxz.97A@cuug.ab.ca> <TYTSO.94Oct31162517@dcl.mit.edu> <MICHAELV.94Oct31211019@MindBender.HeadCandy.com> <TYTSO.94Nov1182557@dcl.mit.edu> <396p13$d0n@news.ycc.yale.edu> Date: Wed, 2 Nov 1994 21:41:47 GMT Lines: 38 In <396p13$d0n@news.ycc.yale.edu> news@remote1-line2.cis.yale.edu (Marc's News Account) writes: >In article <TYTSO.94Nov1182557@dcl.mit.edu>, tytso@athena.mit.edu (Theodore Y. Ts'o) writes: >|> In article <MICHAELV.94Oct31211019@MindBender.HeadCandy.com> michaelv@MindBender.HeadCandy.com (Michael L. VanLoon) writes: >|> >You make a lot of generalizations about 16550-like UARTs that aren't >|> >the real thing and have 1024-byte pseudo buffers. I don't know what >|> >you're talking about since I've never seen such a thing. >|> >|> However, if you're using your Hayes ESP card in 16550 compatibility >|> mode, you're probably not really taking much advantage of your 1024 byte >|> FIFO. It looks good, and sounds sexy; but is actually practical? >|> Probably not. >This is a good point and leads to a question I would like to ask Mr. VanLoon - >given that a 1K buffer does seem a bit excessive for a standard 16550, does the >Hayes ESP card do anything nifty, like FM-0 encoding (230.4Kbps, aka LocalTalk)? >If so, will they tell me how to program it? If this is so, I would be very >interested in such a card. Z85C30's I believe have a similar FIFO as well, and >they're pretty powerful USARTs The Z85C30 is a powerful chip that can do a lot more than a 16450, but the FIFO is not particularly good. It has a 3-byte FIFO on receive, and only one byte on transmit. The Z85230 is a version with a deeper FIFO (8 bytes on receive, 4 bytes on transmit), but it is still not as clever as the 16550A. It cannot be programmed to send one interrupt when the FIFO's exceed a threshold (e.g. half-full) and still interrupt when nothing comes in for some time. Anyway, these chips are good when HDLC and/or encoding (like NRZI or FM-0) is required, but are not especially well suited for plain ASYNC. Rob -- ------------------------------------------------------------------------- | Rob Janssen | AMPRnet: rob@pe1chl.ampr.org | | e-mail: pe1chl@rabo.nl | AX.25 BBS: PE1CHL@PI8UTR.#UTR.NLD.EU | -------------------------------------------------------------------------