Single PLC Lost For Unknown Reason

Event Year: 2003 Reliability: Likely But Unconfirmed
Country: United States
Industry Type: General Manufacturing

A single PLC5 was lost while saving on-line edits using Al software. The potential culprits considered were:

1. An Ethernet broadcast storm
2. ControlNew grounding and/or message overload
3. Processor over-capacity
4. Noise on CH0.

All of the above were deemed unlikely. The only way to clear the processor was to reload the program from disk. The processor is old - PLC5-40C (1.25!) with an ethernet sidecar. Had just completed on-line editing (using AI software), and went to save changes to the hard drive. About 70% of the way through the save process, the processor faulted (solid red light) and the save failed (got a message about a DH+ failure - when programming via ethernet!).

Used about 85% of the available processor memory. Also, the only change to the network in the last 3 years is that the BNC connector that used to plug into the programming PC now plugs into a hub, and the PC now connects to the hub using an RJ-45 connector. Nothing else is connected to the hub.

Have sinced reworked a good chunk of the code and dropped processor utilization down to about 60%, distributed some of the control to other network nodes to allow reduction of about 90% of the ethernet messaging that was taking place, removed the ASCII code that wasn’t being used anyway, reduced the amount of data that the Cnet PanelView’s were polling for, and now do edits on that line only when we are in transition periods (where an ‘unplanned’ shutdown won’t hurt).