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Sintax to use a Pointer declared in a variable table

Created by: Kankuamo at: 2/25/2010 1:37 AM (7 Replies)

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2/25/2010 1:37 AM	Rate (0)
Kankuamo Posts: 16 Rating: (0)	Hello: I'm trying to create an FC where a Pointer is declared in the variable table. Then, use the pointer as reference to point to several bits and bytes. I though it was possible to use and stament like L PointerDeclared LAR1 But the compiler does not accept this. Is it possible to do something similar to this??? What is the correct use of a Pointer when is declared in the variable table? Thanks in advance for your help.
Kankuamo Posts: 16 Rating: (0)
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2/25/2010 7:05 PM	Rate (0)
Aret Posts: 2348 Rating: (259)	L PointerDeclared is not correct - ACCU is 4bytes, POINTER is 6. So you have to load by parts L P##PointerDeclared LAR1 L W[AR1,P#0.0] // first part - db number L D[AR1, P#4.0] //second part - area-crossing 32bit pointer
Aret Posts: 2348 Rating: (259)
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2/25/2010 7:38 PM	Rate (0)
Kankuamo Posts: 16 Rating: (0)	Hello Aret: I was trying that right before you answer, but it did not work, or at least for what I'm trying to achieve. I'm including a screenshot of a simulation of a small program where I'm trying to load a pointer and use indirect adressing. I am entering I0.0 into my pointer, and I was expecting to see the pointer "pointing" to the input memory area, but instead is pointing to the "previous local data". What am I missing??? Attachment screenshot.JPG (816 Downloads)
Kankuamo Posts: 16 Rating: (0)
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2/25/2010 10:54 PM	Rate (0)
Kankuamo Posts: 16 Rating: (0)	I am confused, but I think I find a way to make it work. I declare the adress that I want to point as an Out in my variable declaration. I took another shoot screen of the a test program running on the simulator. Attachment screenshot1.JPG (504 Downloads)
Kankuamo Posts: 16 Rating: (0)
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2/27/2010 6:55 AM	Rate (0)
Aret Posts: 2348 Rating: (259)	1) Supose you have FC1, with input variable x: pointer. When you call FC1 you make x:=I0.0/ 2) Inside FC you want to readvalue from I0.0. Then you need L P##x LAR1 L W[AR1, P#0.0] T #db_num // temp variable OPN DB[db_num] L D[AR1, P#0.0] T #ptr32 // 32bit pointer . Would contain 82000000 LAR1 #ptr32 A [AR1,P#0.0] // here you get value from i0.0
Aret Posts: 2348 Rating: (259)
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8/1/2018 2:32 AM	Rate (0)
AnsuAbinesh Experienced Member Joined: 12/14/2010 Last visit: 4/14/2023 Posts: 116 Rating: (0)	Hi , I am also trying the same way. But i am not getting result as i want. Step 1. I need to read the input address IW100 using as pointer method. If i use P#100.0 directly in the program i can read 100 in the AR1. L P#100.0 LAR1 L IW [AR1,P#0.0] T #Test1 A I [AR1,P#0.7] = #MSB8 Step 2. If i try to read the IW100 using below code but AR1 values are showing v 21.0 instead of 100. L P##Torque_Input // data type pointer LAR1 L IW [AR1,P#0.0] T #Test1 A I [AR1,P#0.7] = #MSB8 Could you please suggest. Thanks in Advance. Attachment Ponter2.JPG (263 Downloads)

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8/1/2018 8:04 AM	Rate (0)
fritz Diamond Expert Joined: 10/7/2005 Last visit: 6/9/2023 Posts: 2969 Rating: (1025)	Hello AnsuAbinesh Pointers are 6 Bytes in length and passed by reference (which means their value is stored in the TEMP memory of the calling Block which is then also referred to as V memory and which is what you see) The fix in your case is as below: L P##Torque_Input // data type pointer LAR1 L D [AR1,P#2.0] // load pointer value from calling Blocks V memory LAR1 L IW [AR1,P#0.0] I hope this helps
	Cheers fritz The advice and opinion given in this thread is that of the author and does not necessarily reflect the views of I S Systems Pty Limited. To find out how I S Systems can help you with your automation needs please visit www.issystems.com.au.
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8/1/2018 10:40 AM	Rate (0)
AnsuAbinesh Experienced Member Joined: 12/14/2010 Last visit: 4/14/2023 Posts: 116 Rating: (0)	Hi Fritz, Tested & working as expected. Thanks for your kind help.

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