I have two MicroLogix 1500 PLCs connected to our control network using ENIs. Both have been working for at least a month but this morning all of the tags for one of them showed as stale. The status of the stale 1500 is “Connected: Protocol: PCCC” while the status of the good 1500 is “Connected: Protocol: EIP”. Rebooting the PLC/ENI had no effect.
Disabling and enabling the device on the Devices page fixed the problem and the protocol is now EIP. Why did this happen and how can I prevent it from happening again?
[quote=“CJVR”]I have two MicroLogix 1500 PLCs connected to our control network using ENIs. Both have been working for at least a month but this morning all of the tags for one of them showed as stale. The status of the stale 1500 is “Connected: Protocol: PCCC” while the status of the good 1500 is “Connected: Protocol: EIP”. Rebooting the PLC/ENI had no effect.
Disabling and enabling the device on the Devices page fixed the problem and the protocol is now EIP. Why did this happen and how can I prevent it from happening again?[/quote]
NET ENIs are notorious for locking up if hammered with too many data requests. The original intention of the NET-ENI module was to allow non Ethernet PLCs message to other Ethernet PLCs.
You may want to create a slower scan class for the ML1500 and look at the PLC program to see if any fast message requests are being performed over Ethernet. Also find if any other PLCs are messaging these PLCs.
In the PLC program I always put messaging using a staggered method, where a cycling timer runs to 2 seconds and resets and repeat.
Then in PLC code stagger message instructions:
Thanks for the quick reply. I have heard nothing but bad things about ENIs but that’s what I am stuck with right now. If you scenario is correct wouldn’t a power cycle get everything back to normal? And why would the device show up as connected and all the tags stale and have Ignition using a different protocol?
This is a machine that I can not change the program so that is not an option. I can change the scan time to reduce the load on the ENI if I have to.
What other options are there to connect a MicroLogix 1500 to Ignition?
[quote=“CJVR”]Thanks for the quick reply. I have heard nothing but bad things about ENIs but that’s what I am stuck with right now. If you scenario is correct wouldn’t a power cycle get everything back to normal? And why would the device show up as connected and all the tags stale and have Ignition using a different protocol?
This is a machine that I can not change the program so that is not an option. I can change the scan time to reduce the load on the ENI if I have to.
What other options are there to connect a MicroLogix 1500 to Ignition?
Thanks again.[/quote]
You are stuck with what you have unless the ML1500 is swapped out for a 1400 ( ethernet based ). Check the baud rate of the DF1 port on the ML1500, make sure it is as fast as possible. Be aware the Net Eni is an ethernet to serial converter, so the bottle neck is the speed of the serial link.
[quote=“CJVR”]Thanks for the quick reply. I have heard nothing but bad things about ENIs but that’s what I am stuck with right now. If you scenario is correct wouldn’t a power cycle get everything back to normal? And why would the device show up as connected and all the tags stale and have Ignition using a different protocol?
This is a machine that I can not change the program so that is not an option. I can change the scan time to reduce the load on the ENI if I have to.
What other options are there to connect a MicroLogix 1500 to Ignition?