Comm issues

Alright I have 4 micrologix 1500 (nodes 2,3,4,and 5). Going to (4) 1761 net-aic. Also another net-aic going to a 5/04. Hook up to dh+ , go pass through and everthing looks and runs fine. Remove power to a micrologix and my messaging starts to return incorrect values. The values get worse as you power down more micrologix. There are message writes in the 5/04 to each micro. There are reads and writes in each micro going to the 5/04. All parameters have been triple checked in all the message blocks.

It also seems that if a micro messaging "freezes" the incorrect values start to appear.

Any Ideas. This is driving me nuts!!!!!

I added logic in the micro's to kick start the messaging if it stalls for more then 5 seconds.

I have not lengthed the time between messages in the 5/04 because when it works it works fine. It'll run for days before the values get weird and we kick start the messaging again, that why I added kick start logic.

Occasionally a micro has to be powered down for servicing the unit so I need a resolution but I out of ideas.

Enough rambling.


HELP!!!!!



Thanks
Drewcrew6

... my messaging starts to return incorrect values.

Click to expand...

Do you mean the messaging initiated in the SLC-5/04, or in the MicroLogix ?

This points to the issue being in your SLC-5/04 messaging application logic, not on the network. It's extremely unlikely that the actual message data is getting corrupted and yet the MSG blocks are successfully completing (which indicates a correct CRC error check on the packet).

What does your SLC-5/04 message logic do when a message to a MicroLogix fails ? Does it go on to the next MicroLogix, or does it re-try ? If it skips over the node to which messaging failed, how long does it wait before it tries to message to that node again ?

I'm also not sure why you have MSG reads in the Micro1500 and MSG writes in the SLC-5/04, unless they're for data that changes on an event, rather than periodically. What's the theory behind your communication strategy ?

message problems

I am not sure exactly what is happening, but you may be getting a buffer overflow problem especially if relying on timers for your MSG blocks when 1 processor shuts down.

There has been a lot of discussion about MSG blocks here, do a search on MSG or message and you can find some good examples.

The message writes in the 5/04 are timed and sequential. When a micro is powered down the messaging errors.

In the micro's the read updates certain values, one value is okay to write which triggers the write message.

I don't have the code at home so monday night when I go back in I will check how long the timer is for the 5/04 messaging.

Thanks
Drewcrew6