Wireshark-bugs: [Wireshark-bugs] [Bug 7337] EtherCAT dissector: datagram header interprets some
Date: Tue, 26 Jun 2012 03:35:29 -0700 (PDT)
https://bugs.wireshark.org/bugzilla/show_bug.cgi?id=7337

--- Comment #5 from [email protected] 2012-06-26 03:35:28 PDT ---
Hi !

I manipulated the source code of an open source ethercat master in a way, that
the master itself sends datagrams with the enabled cyclic-bit. I implemented
both possibilities of the cyclic bit position to examine which one is the
correct, i.e. which possible bit position has to be set to 1 so that the slaves
react.
According to the specification the slave should destroy the packet if the
cyclic bit is recognized and no outputs should be changed for safety reasons.

So much for the theory...

Surprisingly my setup with some Beckhoff terminals did not react either to the
"RRCRM" or to the "RRRCM" bit pattern in the datagram. In both ways my outputs
where enabled, so I cannot state which one of the given possibilities is the
correct one.
In the attachment "trace with both pissible bits set to 1" 4 packets were
extracted from a trace, where both possible cyclic bits are set so you can see
which bits I used for my tests.

We also have some hilscher terminals for testing purposes at our lab, but these
terminals are integrated in another project right now. If I get a hand on one
of them I'll test them as well.

Maybe someone else has some other terminals (with another protocol
implementation) and can test it?

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