Modicon PLC - OverRun Error

[GeoffC]

The cables are known as the communications bus
Do you have terminators at each end of the rio cables. One at the end of the cable where the head module is and one at the end of the cable where the last card is connected

 

[GeoffC]

At each RIO drop connector is the cable for the drop connector to the module a minimum of 1 metre in length

 

[macs_plc]

The Last Drop is connected with the Terminator, but i could find any terminator or option for the terminator at the end of the cable where the head module.

For better understanding i have attached some pictures how my panel looks like, please have a look at it and let me know your thoughts....

 

[GeoffC]

Cant really see how the RIO network is cabled from your pictures

Here is a link to the RIO installation guide
http://www.barr-thorp.com/wp-conten...-Cable-System-Planning-Installation-Guide.pdf

from that guide - note that each connector to a card must be through a tap, and the head module must be at one end of the bus and at the other end of the bus the last tap must have a line terminator fitted (see page 21 for a diagram)

 

[Bit_Bucket_07]

Thanks Brendonh.....
Ya it is working and functioning....
Will have a look at the IO error details and come back to you...

Your remote I/O system is operating properly, in spite of these overrun error indication bits being set, is that correct? Is it possible that these bits were set while a remote chassis was powered down, and that they merely reflect a fault condition that occurred in the past, or should the error bit clear when the overrun error no longer exists? It might be that the alarm bits latch after an error and you have to either reset them with program logic, or by restarting the processor. Channel errors on unused analog channels are not uncommon. I wouldn't worry too much about those.

 

[GeoffC]

Bit_Bucket is exactly right, if at some stage you had an overrun error you must clear %S19 (either by program or animation table) to clear the error

 

[macs_plc]

@ Bit_Bucket_07: Its right - As you said "remote I/O system is operating properly, in spite of these overrun error indication bits",

"alarm bits latch after an error" - I hope this may be the issue here...

Bit_Bucket_07 & Geoff C....I will try both of your suggestions and let you know

 

[macs_plc]

Overrun Error resolved by restarting the PLC one by one...(restarted Standby first and changed to Primary, the same has been done for the other PLC)

Thank you Brendonh, Bit_Bucket_07 & Geoff C for sharing your experience.....

Is there any preventive measures there... to avoid the same error in future ???

 

[GeoffC]

Is there any preventive measures there... to avoid the same error in future

Yes - an overrun error is normally caused by network issues - check the cabling is as per the document I posted earlier. Especially check terminators in place, each drop cable (from the T to the card) is a minimum of 1 metre in length
Also - add code to bring up the alarm AND then reset the %S bit (%S19) to clear the fault

 

[macs_plc]

Hardware Configuration are all correct as per the document...
Will do some additional code to reset the Bits....

Thank you all for your valuable comments ....