Chapter 12. DiagnosticsGFK-2224Q January 2017 239Accelerated EGD Consumption Can Interfere with EGD ProductionConsumed EGD exchanges received from the network normally receive accelerated processing for increasedoverall EGD performance. This accelerated processing can preempt EGD production activity, possibly delayingtransmission of produced exchanges to the network. Such delay varies with network loading and the volume ofconsumed exchanges. In applications requiring minimal produced exchange timing variability, the consumedexchange acceleration may be disabled via the “gc_accel” AUP parameter. (See Appendix A for details of the“gc_accel” parameter.) Under extreme network load, accelerated processing of the incoming EGD samplesmay consume so much processing time that the watchdog timer for the network interface expires and thenetwork interface is reset.Channels Operation Depends Upon PLC Input ScanningCommunication channels operation always includes updating the Channel Status Bits (located within theEthernet Status data) into PLC memory, which occurs when the PLC scans inputs from the Ethernet module. Atleast one PLC input scan must occur for each data transfer on a channel, so the channel can run no faster thanthe PLC scans the Ethernet Status data. When the Ethernet interface is configured to use an I/O Scan Set thanruns more slowly than the PLC sweep, each channel must wait until the next time that its scan set runs totransfer its Channel Status bits. This can reduce channels performance.If the Ethernet interface is configured to use an inactive I/O Scan Set, the Channels Status bits will not betransferred and channel operations will not complete.
