[etherlab-users] Redundancy support

[Gavin Lambert]

Yesterday, I quoth:
> 2. There appear to be a few things that only seem to work on the main
link,
> not the backup link (unless I'm missing something).  Register requests
(maybe
> only some types?) seem to be one of them, and I'm dubious about the DC
sync
> behaviour as well -- I don't think the RMW broadcast sync to the refclock
is
> really going to work on a link that doesn't contain the refclock.  The
> transmission delay measurements seem incorrect too.

As an example of this, here are some excerpts of "ethercat slaves -v" in
various states with two slaves.

This is a "normal" chain network -- backup link not connected:

=== Master 0, Slave 0 ===
Device: Main
  Distributed clocks: yes, 64 bit
  DC system time transmission delay: 0 ns
Port  Type  Link  Loop    Signal  NextSlave  RxTime [ns]  Diff [ns]   NextDc
[ns]
   0  MII   up    open    yes             -    114873362           0
0
   1  MII   up    open    yes             1    114874642        1280
640
=== Master 0, Slave 1 ===
Device: Main
  Distributed clocks: yes, 64 bit
  DC system time transmission delay: 640 ns
Port  Type  Link  Loop    Signal  NextSlave  RxTime [ns]  Diff [ns]   NextDc
[ns]
   0  MII   up    open    yes             0    644914350           0
640
   1  MII   down  closed  no              -            -           -
-

This is exactly the same network with the backup link connected but not
needed (no break in the main network):

=== Master 0, Slave 0 ===
Device: Main
  Distributed clocks: yes, 64 bit
  DC system time transmission delay: 0 ns
Port  Type  Link  Loop    Signal  NextSlave  RxTime [ns]  Diff [ns]   NextDc
[ns]
   0  MII   up    open    yes             -   3165080514           0
0
   1  MII   up    open    yes             1    114874642  1244761424
622380712
=== Master 0, Slave 1 ===
Device: Main
  Distributed clocks: yes, 64 bit
  DC system time transmission delay: 622380712 ns
Port  Type  Link  Loop    Signal  NextSlave  RxTime [ns]  Diff [ns]   NextDc
[ns]
   0  MII   up    open    yes             0   3692590109           0
622380712
   1  MII   up    open    yes             -   1829843904  2432221091
0

And here it is with a break between the two slaves:

=== Master 0, Slave 0 ===
Device: Main
  Distributed clocks: yes, 64 bit
  DC system time transmission delay: 0 ns
Port  Type  Link  Loop    Signal  NextSlave  RxTime [ns]  Diff [ns]   NextDc
[ns]
   0  MII   up    open    yes             -   4023995730           0
0
   1  MII   down  closed  no              -            -           -
-
=== Master 0, Slave 1 ===
Device: Backup
  Distributed clocks: yes, 64 bit
  DC system time transmission delay: 0 ns
Port  Type  Link  Loop    Signal  NextSlave  RxTime [ns]  Diff [ns]   NextDc
[ns]
   0  MII   down  closed  no              -            -           -
-
   1  MII   up    open    yes             -    519954610  1122331797
0

Possibly some of this is related to the weird linked-but-not-linked
behaviour when the backup link is connected but unneeded (described in my
prior email).