Hello fellow Automation folks!

I'm new to MRP and having some trouble understanding some things about it.

I've read where it should take on the order of 200 milliseconds for an MRP loop to detect a break and re-route messages the other way around the loop.  But when I test the setup I have here, it seems to take about 5 seconds for the bus to recover and data to start coming into the PLC again.

I wondering if I have something configured wrong?  

I've attached a picture of the Topology and the Domain Management views of the configuration that I'm using. 

I'm using an S7-315 2 PN/DP for my tests.  I have the MRP loop connected to both Ethernet ports, and am monitoring the program data over the USB MPI link.  Programming package is Step 7 V5.5 SP3.

The details of what I'm seeing are:

1.  When I break the loop in one direction, the interrupt is almost unnoticeable.  However, when I re-connect the break, the devices will drop offline for about 5 seconds.  Is this normal?

2.  When I break the loop in the other direction, the devices drop offline for about 5 seconds.  When I reconnect the break, the devices drop offline again for another 5 seconds.  This one surprised me the most.

3.  When the communications drop out, the SF and BF2 lights will flash on the PLC.  When the communications re-establish, the lights go out.  This all seems to line up with what I'm seeing happening to the data as the links re-establish.

One last thing - on the domain management view, the form doesn't seem to remember that I've selected "MRP domain" for the Display radio buttons.  Could this indicate that I've set something up wrong?

Thanks in advance for any comments and guidance!

Try this...

Connect

  IND570-1 (Port2) to IND570-2 (Port2)

  IND570-2 (Port1) to IND570-3 (Port1)

and keep the rest same.

Thanks for the suggestion PSW2586!

The picture you made must have taken some time, and I appreciate the effort!

When I tried your suggestion, the System Fault light comes on and stays on, and the loop breaks still react the same way as before.

I THINK what is going on is that the program needs an OB block defined in order to not throw an error.  But I can't find anything that tells me which OB block that would be.  I've tried OB40, OB70, OB82, OB83, OB86, and OB122 (and some others that apparently were not intended for the S7-315).  But there is no change in the system response.

I've gotten confirmation that the devices worked when tested at PI.  So, I'm pretty sure that I'm dealing with a programming or configuration issue.

Any ideas out there from someone more savvy with Siemens PLC's than I am?

Finally got to the bottom of this!  But it took some help from two other suppliers to do it.

It turns out that the problem was that the Device Watchdog timers were set lower than the 200 millisecond recovery time for the MRP loop.  As a result, when a break took place, the Watchdog timer would trip and cause the device to fault.  It took about 5 seconds for the device to recover from that fault.

Details:

In the hardware configuration, double-click on the slot "X1" line  "Interface" module of the Device.  Then click on the "IO Cycle" tab.  In the frame for the "Watchdog Time", click on the dropdown box and select the number of I/O updates that the device can accept with missing I/O data.  The time (shown on the next line below) is calculated as this number multiplied by the Update Time (see the "Update Time" frame right above the "Watchdog Time" frame).

Make sure that the total Watchdog time is GREATER than the 200 millisecond recovery time for the MRP loop.