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Hi all,
I have an analog card (331-7KF02-0AB0) and a 315-2 PN/DP cpu.
I'm reading my analog value with a pheriperal address (PIW) and i'm noticing that the digital value is 32767 during the first real plc scan (the first scan that OB1 is executed). One scan later the analog value is measured correctly (e.g. 27680).
Can somebody explain why this is happening and if this is avoidable? Since i'm using a pheriperal address, i would assume that the plc would immediately have the correct value but it seems to be one scan later.
I'm generating an alarm in my code when the analog value overflows (32767) so each time the plc restarts (e.g. after a power cut), i get an alarm on all my analog values being out of range. Is there any elegant way to solve this. I want to be sure that the plc is working with the correct analog values when it goes through OB1 for the first time.
Many thanks for any helps.
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