My head hurts

[TOMC]

I am working on a press that has a micrologix 1500 and a panel view 300. My problem is that sometimes some of the alarms are not being displayed. This program was written by the integrator and I am piecing my way through his alarm routines. My question is when does the panel view read the tag, end of scan or anytime and how long does it need to see it.

Thanks

Tom

 

[Tharon]

Depends on the com setup of the Panelview. Some connections are slow and will take a while to update tags, and if a tag changes back and forth before the update it will be missed.

 

[bernie_carlton]

IF it reads the alarms then it will be between scans. But there's no guarantee that this will happen EVERY scan. If the alarms are grouped as bits in contiguous words you have the best chance of having them read as fast as possible.

 

[sthompson]

Tom:

Communications will normally be serviced at the End of Scan.

See Chapter 21 of this Manual for information about improving the Communications Throughput.

http://literature.rockwellautomation.com/idc/groups/literature/documents/rm/1762-rm001_-en-p.pdf

Stu....

 

[TOMC]

I knew it was at the end of scan I just needed someone else to say it. Plus I wanted to make sure there was nothing funny going on. I am sure that alarm bits are being dropped and I am going to have to hold them high longer. Thanks for the replies I just needed to have my brain rebooted.

Tom

 

[nwboson]

Use a simple semaphore to ensure that anything the PLC says is seen by the HMI: the PLC sets a latch (alarm condition), the HMI clears the same latch once its seen it. Now the speed of the two separate processes is immaterial...