Messages in this thread | | | Subject | Re: serial.c (half duplex support) | Date | Wed, 27 Oct 1999 12:49:24 +0100 | From | David Woodhouse <> |
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rhw@MemAlpha.CX said: > I'd have to describe the protocol as broken in that case, and only > completely implementable in hardware rather than in software.
Which, given that it's a fieldbus, and is designed specifically for communication with dedicated hardware, is not exactly unreasonable.
rhw@MemAlpha.CX said: > Just a thought, but "33 bit time periods" sounds like 8E1 or 8O1 and > "3 character periods". If such is the case, it shouldn't be hard to > handle. Let me go back to my original specification, and I'll reply to > that with additional comments including what I see for this...
Definitely 3 character periods. 8E1 IIRC - sorry, I thought I'd said that earlier.
rhw@MemAlpha.CX said: > > Note "shall be", not "may be" or "should be". My interpretation > > of that is that the receiver is required to detect it, yes. > My interpretation of that is that it is written in LEGALESE, and in > the said language, "may" and "should" do not exist since they are > considered to be too vague.
Not at all. 'Should' indicates something which an implementation ought to do, but it won't fail the certification if it doesn't. Likewise, loosely speaking, 'May' indicates something which an implementation isn't expected to do, but it won't fail the certification if it does.
It's quite common to use such words in this kind of specification. RFC1122 for example, defines MUST, SHOULD and MAY in section 1.3.2:Requirements
(grep --context=23 \"SHOULD\" /net/src.doc.ic/public/packages/rfc/rfc1122.txt)
rhw@MemAlpha.CX said: > In other words, if Lose9x can't handle it, the bus is not likely to > succeed in its current form, so I would watch out for sudden changes > to the specification to enable said OS to support it.
Sorry, I misunderstood you there. I see your point, but (unfortunately?) there are intelligent cards available which provide such support on Windows. It's not absolutely necessary to use commodity hardware for the bus to succeed commercially.
It _is_, however, highly desirable to be able to use commodity hardware for the Linux support, as well as the intelligent IO cards (for which I already have one driver in 2.3.current)
---- ---- ---- David Woodhouse David.Woodhouse@mvhi.com Office: (+44) 1223 810302 Project Leader, Process Information Systems Mobile: (+44) 7976 658355 Axiom (Cambridge) Ltd., Swaffham Bulbeck, Cambridge, CB5 0NA, UK. finger dwmw2@ferret.lmh.ox.ac.uk for PGP key.
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