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mhowasso

Micrologix RTC Second Status Bit

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Hi All... I hate to bother you all again, but I have another question. Im swapping out some more SLC100 and PLC2 to a Micrologix 1500 using RSLogix 500 software. In using a PLC5 with RSLogix 5 software there is a status bit for RTC Seconds of S:23/0. I am not having any luck finding a similar status bit in RSLogix 500. Any suggestions..?????? As always..THANKS..!! Mark

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The RTC for a ML1500 is an optional add on module. Do you have one? If so then the info is available thru the RTC function file and the status files. But you need the module first. There is a free running clock. See ststus word S:4. See PDF below FreeRunningClock.pdf Edited by Mickey

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mhowasso, Did you have a comment? If so it didn't get posted.

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On some of the MicroLogix models, the Second value in the Real Time Clock is not accurately updated ever single second; sometimes you will see it "miss" a second and then "jump ahead" two seconds. This is caused by the operating system reading the RTC asynchronously. Therefore you can say that the accuracy of the Real Time Clock in a MicroLogix 1100 is two seconds. This is not a big deal if you are doing time-of-day events, which is the point of the Real Time Clock. But do not try to use the RTC to create a 1-second timer. Use a timer.

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Edited by slcman

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Thanks guys, I tried the RTC and I see what you mean. I just used a couple of TON like you suggested. Thanks Again.

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Good for you. Timer do the job but keep in mind STI interrupt is more accurate.

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