12/7/2009 4:35 PM | |
Posts: 103 Rating: (11) |
How are you all I want to use temp to make memory map -transfer input bits to marker bits- but I have strange problem , that temp memory area keep its value as it is even if the source value changed !!!!! in the attachmentyou will find picture to describe the situation I assume that temp value should return to zero when the source value return to zero but it doesn't want to return to zero ,, why??? thanks Attachmenttemp2.zip (127 Downloads) |
12/8/2009 12:32 AM | |
Joined: 10/7/2005 Last visit: 10/19/2024 Posts: 3024 Rating: (1054)
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Helloahmedmae94 your problem is caused by doing a READ access to a TEMP variable before youWRITE to it (I could open the zip file, don't know why billwest had the problem). TEMP variables are only "valid" while the Block is executed and do NOT retain their valuefrom one call of an FC/FB/OB to the next one. As such the "Golden rule" for usage of TEMP'sis: You mustinitialise them (i.e. WRITE to them before you READ fom them). By the way, Distributed safety software checks for adherence to this rule in F-LAD and F-FBD and complains if it is not followed, "normal" Step7 does unfortunatelyNot "complain" if the rule is violated (and there's plenty of forum questions relating to this subject so you are not the first to fall into this "trap" and probably won't be the last either). Possible solutionsfor your problem are: 1.) Use an IN_OUT variable to which you assign an Memory or Datablock Doubleword (if you intend to create a reusable FC/FB). 2.) Use an Memory or Datablock Doubleword instead of a TEMP variable inside the FC (if your FC/FB is not meant to be reuseable). 3.) "Convert" your FC to an FB and use a STAT variable instead of a TEMP variable. I hope this helps |
Cheers |
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12/8/2009 9:49 AM | |
Posts: 103 Rating: (11) |
I'm so sorry , first : I want to thank fritz & billwest second :thisis the code L IB 0 SLD 24 L #temp2 OD T #temp2 L IB 1 SLD 16 L #temp2 OD T #temp2 L IB 2 SLD 8 L #temp2 OD T #temp2 L IB 3 SLD 0 L #temp2 OD T MD 20 >>>>and I have modificated the file and reuploadedit again third: the previous code work properly without any problems in aparticular software in chemical plant , but the problem occur only when I'm coping this code to new software (new project)that I have made to test strange codes thanks Attachmenttemp2.zip (132 Downloads) |
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