12/3/2009 12:26 PM | |
Joined: 11/22/2009 Last visit: 10/20/2022 Posts: 11 Rating: (0) |
One of the causes of stopping the PLC could be that the number of errors you had at a punctual time provoke multiple calls to the concerned OB (i.e.: OB82) and then the time of processing those interrupts overpass the "watching cycle time" of the PLC, and then it will turn on STOP mode. We're experiencing this issue and I was wondering how we could prevent this behaviour. For example using th SFC 39 to inhibit the lauch of certains OBs in case of problem, but the drawback is that we will not have such events recorded and then be a little bit blind to what concerns to diagnostics.... Is there any other way to prevent the PLC passing to STOP whenever there is an avalanche of errors and then diagnostics? Thanks, |
12/17/2009 4:58 PM | |
Joined: 1/4/2008 Last visit: 9/23/2024 Posts: 703 Rating: (96) |
Hello Quike, sorry for late response... I don't know the solution which could fully satisfy your request, only I could suggest is to combine the discussed things. You can set the scan cycle monitoring time so you could increase the value (up to 6s).In some cyclic interrupt (e.g. OB35 with 100ms scan) you can check the actual cycle time (by counting which is reseted at OB1 start or by comparing the time tick) and if the value comes near the presettedmonitoring time then you can use that SFCs to mask the interrupts and prevent CPU from change themode to stop because of this reason. You should of course release the interrupts again. In this case you will loose some of the diagnostics interrupts, but the CPU stays running. You could also create the user message to the diagnostic buffer (with the SFC 52 "WR_USMSG")with some additional infoin case of masking the interrupts. Regards Sydney |
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