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Temp Variable In FC malfunctions

Created by: ashishm at: 7/7/2013 4:23 PM (21 Replies)

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7/7/2013 8:27 PM	Rate (0)
yy1 Gold Member Joined: 3/24/2009 Last visit: 1/20/2021 Posts: 532 Rating: (109)	I wouldn't call it malfunction. I'd say, that it's a wrong usage. I think, that you'll find the best posting to this topic in this thread (posting of fritz) Best regards, yy1

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This contribution was helpful to 3 thankful Users jacek d fritz IBN-Service

7/7/2013 8:32 PM	Rate (0)
IBN-Service Posts: 8946 Rating: (989)	yy1 I wouldn't call it malfunction. I'd say, that it's a wrong usage. I think, that you'll find the best posting to this topic in this thread (posting of fritz) Best regards, yy1 Perfect!
IBN-Service Posts: 8946 Rating: (989)
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7/8/2013 8:01 AM	Rate (0)
viralpatel Silver Member Joined: 11/18/2010 Last visit: 2/10/2021 Posts: 522 Rating: (31)	IBN-Service MRG When you call FC for one time, your program work properly. ... That is not correct because Temp Variables may be influenced from other FC, FB and OB also!!! Hi, i had also faced same problem during one of my project software development, so, havecreated whole new project to check whats wrong i am doing in PLC Logic and just includedFC1/FC2 calling one by one in OB1 and in FC -2 temp variable assigend means in FC1 Temp1 /Temp2 and in FC2 Temp2/Temp3 and and just make set first variable Temp1 in FC1 it will automatically make Temp3 bit set In FC2 without satisfying condition to make Temp3 on,so i was amazed and replaced all temp with M bits. i could not found the reason , so i want to know what will be my mistake in creating this type of logic, regards, viral patel

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7/8/2013 4:30 PM	Rate (0)
jacek d Platinum Member Joined: 9/23/2005 Last visit: 2/24/2021 Posts: 3166 Rating: (502)	OMG. There's nothing else to say... Pls RTFM. In this case about differences beetwen FCs and FBs. That's really basics. Without this you will get amazed constantly. Over and over.
	Regards, Jacek What is confusing you is the fact that you never see a number but always its digit representation. So you end up thinking that the number is the representation. - Andrej Bauer Any claims against me - based on whatever legal reason - resulting from the use of any code and/or ideas presented on this forum shall be excluded.
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7/8/2013 8:56 PM	Rate (1)
P_PANDE Advanced Member Joined: 5/9/2012 Last visit: 10/23/2020 Posts: 72 Rating: (6)	In this case u can use memory words to transfer the temp words. Means at the first network of fc use move from mw to temp & at the last network use temp to mw again & define the address of mw as inout during block call. Now u can monitor temp using these mw defined at that perticular block call.

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7/10/2013 8:46 AM	Rate (0)
pman Posts: 57 Rating: (1)	For addressing a peak, you cannot use a temp variable for the operand that performs the peak, but only for the Impulse operand and this will be on only as long as you are in the current FC, so it will be a pulse that lasts a few networks, not even one scan. For the peak function, you cannot use a temp variable because the peak function has to sense the difference of the signal between two contiguous scans. In order to do this, it has to save the RLO of the signal from the previous scan. If the variable is temp, then after exiting the FC, this bit will reset irrespective of the value that it had during the running of the FC. So in the next scan this bit will be again 0 and if the real value of the signal is still 1, then the peak function will understand that again there is a change of value and will consider it as a new pulse and so the impulse operand will still be on! And this will go on forever, so long as you're using a temp variable for the peak function and as a result the impulse operand will stay on as long as the RLO of the peak function is on.
pman Posts: 57 Rating: (1)
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12/30/2016 11:56 PM	Rate (0)
mohittyagi Posts: 2 Rating: (0)	OPN #RDCB L DBD216 T MD200 OPN #CRDB L MD200 T # WRAP This FC called many times. I want to know that can we use MD 200 as temporary storage in this FC and can use at other place for other use.
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1/2/2017 9:01 AM	Rate (0)
jacek d Platinum Member Joined: 9/23/2005 Last visit: 2/24/2021 Posts: 3166 Rating: (502)	Basically - yes. Unless it's in different threads (i.e. OBs) than the one where you call your FCs (if it's only one...) But why don't you create dword variable in your FC interface and use it instead?
	Regards, Jacek What is confusing you is the fact that you never see a number but always its digit representation. So you end up thinking that the number is the representation. - Andrej Bauer Any claims against me - based on whatever legal reason - resulting from the use of any code and/or ideas presented on this forum shall be excluded.
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1/3/2017 12:36 PM	Rate (0)
mohittyagi Posts: 2 Rating: (0)	Thanks sir But if this FC will call in two program then data moved in MD 200 will malfunction. Please clear it
mohittyagi Posts: 2 Rating: (0)
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1/3/2017 1:10 PM	Rate (0)
jacek d Platinum Member Joined: 9/23/2005 Last visit: 2/24/2021 Posts: 3166 Rating: (502)	Let's suppose that the code below is executed in OB1. OPN #RDCB L DBD216 T MD200 //and let's suppose that MD200 gets value of 1000 Then here comes e.g. a timed interrupt OB35 and also uses MD200 like below. L 100 T MD200 //so, here value of 100 is written to MD200 Now execution returns to the OB1 and starts from the point it was interrupted. OPN #CRDB L MD200 T # WRAP Now guess what is written to #WRAP. And this is error very hard to trace as it happens by coincidence.
	Regards, Jacek What is confusing you is the fact that you never see a number but always its digit representation. So you end up thinking that the number is the representation. - Andrej Bauer Any claims against me - based on whatever legal reason - resulting from the use of any code and/or ideas presented on this forum shall be excluded.
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