[etherlab-users] a puzzle about igh ethercat master

[Gavin Lambert]

This is normal.

 

The master stack does some housekeeping to determine the number and state of
all connected slaves even with no application running.  This is the sequence
that you are seeing here, when you have one slave connected.

 

As for why it’s an FPRD datagram instead of an APRD as you might have been
expecting, this is because the master also automatically assigns station
addresses (not the same thing as aliases) to each slave as first
encountered.  This prevents accidentally talking to the wrong slave if the
network topology changes before the master can detect this.

 

If you want to see this happening, you will either need to start capturing
earlier (probably not possible if you’re using the debug interfaces on the
same machine, since you won’t be able to react fast enough) or force a
rescan while you’re capturing either via the command or by changing the
topology.

 

From: etherlab-users [mailto:etherlab-users-bounces at etherlab.org] On Behalf
Of ???
Sent: Wednesday, 18 November 2015 19:39
To: etherlab-users at etherlab.org
Subject: [etherlab-users] a puzzle about igh ethercat master

 

Hello, I am learning about the ethercat protocol and using igh ehtercat
master, but have a puzzle.
I connected my slave and just start the igh master by using "ethercat start"
command and no other user app run.
then I use wireshark to capture packet, result like the following picture:

I know it is scaning slaves all the time, but how about this FPRD datagrame,
I haven't see any write cmd to set the slave position to the slave
register。
so, this is my puzzle, I need some tips, thank you in advance!

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