[etherlab-dev] Slave to Slave communication

Florian Pose fp at igh-essen.com
Fri Apr 25 10:42:52 CEST 2008

On Wed, Jan 30, 2008 at 05:03:38PM +0100, Thomas Elste wrote:
> > Moreover, I have not engaged in this, and don't know, what is necessary
> > to make slaves communicate with each other... Do you have more
> > background information than I do?
> Not that I'm aware of. In principle, nothing more should have to be done
> than to tell the relevant slaves to read/write from/to the same logical
> address by configuring the sm/fmmus accordingly. Everything else should
> then depend on the bus topology. Afaik this is the theory, :).

I spoke to a few people about this, in the meantime. The general way to
allow slave to communicate with each other is simply to exchange their
Pdos as usual and to copy the data of the sending slave into the data
range of the receiving slave. At least this is the way,
Safety-over-EtherCAT (FSoE) is operated.

Your proposal is possible, in principle, but it depends on the bus
topology, as you said. The master currently has no interface for this.
The current implementation provides disjunctive logical process data
ranges for each slave, by default.

Best regards,
Florian Pose


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