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SubjectRe: serial.c (half duplex support)
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rhw@MemAlpha.CX said:
> If it can, it should be escaped, perhaps similarly to how it's
> handled in the HDLC protocol (itself an ISO standard) in byte mode

No, as far as I can tell, it's not. You know the length of the packet, and the
stop character is there just as a check.

rhw@MemAlpha.CX said:
> HDLC does not use a length field, but does have the procedure above
> to ensure unambiguous detection of both start and end of field.

Instead of this, Profibus uses an idle time of 33 bits to ensure unambiguous
detection of frame boundaries. Therefore, I'd like to be able to find out from
the hardware driver when such an idle period happens.

Isn't this where we started off?


rhw@MemAlpha.CX said:
> > 2. Each action frame shall be preceded by at least 33 line
> > idle bits (Syn Time).

> > 4. The receiver checks..the Syn Time in the case of an action frame.


> Do the reception rules actually require the detection of the Syn Time
> period, or is that just there to give the receiver time to settle
> down?

> > If the check fails, the whole frame SHALL BE discarded.

Note "shall be", not "may be" or "should be". Mu interpretation of that is
that the receiver is required to detect it, yes.


rhw@MemAlpha.CX said:
> Is the specification available on the web anywhere?

There are some docs on http://www.profibus.com/ but not the complete ones. You
have to be a member, or pay for them. I took the latter route, and only have a
hard copy.


rhw@MemAlpha.CX said:
> To be honest, it's probably not going to be available on ANY
> multitasking system - especially not on Macrohard's LoseSleep 9x
> offerings...

That doesn't mean that it can't be done on Linux. If it's physically possible
to do it with the hardware in question, then I expect Linux to be able to
support it. My expectations of Windows, while they appear to match yours, are
irrelevant.

---- ---- ----
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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