Messages in this thread | | | Subject | Re: serial.c (half duplex support) | Date | Mon, 25 Oct 1999 10:54:30 +0100 | From | David Woodhouse <> |
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rhw@MemAlpha.CX said: > > > An idle time of more than 27 bit times (3 chars) on the wire > > signifies the end of an incoming packet, so the callback (a) > > would be necessary even when there's nothing waiting to > > transmit.
> That sounds like part of your particular line discipline, rather than > a generic part of all half duplex protocols?
Indeed. But the information needs to be made available by the serial hardware in order that my line discipline can behave correctly.
rhw@MemAlpha.CX said: > That should be part of the RS485 protocol itself, in one of two > formats:
<deletia>
> Again, refer to the sources mentioned above.
I am referring to: "Normative Parts of PROFIBUS -FMS, -DP, -PA according to the European Standard EN 50 170 Volume 2", Edition 1.0, Profibus Nutzerorganisation e.V. (PNO), March 1998.
As far as I recall (it's been a while since I actually read it), it says that the end of a packet is signified by an idle time of 27 bit times on the wire. Therefore, I would like some way to find out from the serial hardware when such an idle period happens.
I don't expect this to be used by all line disciplines, but I would like it to be made possible by whatever API we decide upon.
---- ---- ---- 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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