STEP 7 / STEP 7 Lite
SFC 14 DP Read Data Flickering Problem
Thread Starter: USM Started: 6/15/2012 3:27 PM Replies: 4
6/15/2012, 3:27 PM
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Hi there,
I am facing problem in reading DP device data with the help of SFC 14, I called SFC 14 in simple function and that function is being called in OB1. I am able to monitor the Data from the device in Data block, but the problem is that after 10 to 15 seconds data flicker for about 500 mili seconds. Mean suppose the actual data is 200 and for 500 mili seconds it gose to 16 and then come back.
For varification i made a VAT and monitor the Data Block value and the Direct PIW value, the direct value is perfect never flickerd but the data block value flickers it means there is something wrong with SFC 14.
Could you please suggest me that what could be the error in my programm or there is any special way to use SFC 14.
Thanking in Advance.
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6/15/2012, 7:02 PM
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Joined 3/15/2008
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Is there any error message from SFC14?
Do you do unconditioned call?
Are you shure that data provided from SFC14 is corrupt?
Perhaps you overwrite the data from some other program part?
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Thank you for this post from:
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6/16/2012, 6:59 AM
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I monitored three value in VAT,
1.Data block value one word.
2.Direct PIW, same word that i used to monitor in data block.
3.Returen Value of SFC14. which is always W#16#0000
Only data block's word flickers after some time for the period of miliseconds.
For your information, i only used one SFC14 in my whole programm for testing purpose there is no other program. Only OB1, FC1, DB1, and SFC14.
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6/16/2012, 8:40 AM
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I have solved this problem by PLC memory Clear/Reset and then again downloaded the programm, I've monitored data for long time now it is good,
Thanks for the suggestion.
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Thank you for this post from:
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6/16/2012, 11:01 AM
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Perhaps, in background there was still an OB35 "spookying"?
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