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Using POINTER data type

Created by: jboti at: 6/8/2010 10:43 AM (6 Replies)

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6/8/2010 10:43 AM	Rate (0)
jboti Experienced Member Joined: 6/8/2007 Last visit: 9/9/2024 Posts: 53 Rating: (3)	Hi all, A POINTER can be used as input parameter and then it can be assigned in the following way: CALL FC 1 IN0:=P#DB500.DBX 10.0 //IN0 of type POINTER In this case a compiler takes care of correct passing data. Otherstory is accessing data indirectly. A POINTER data type is not suitable for this. I have seen the above on many places throughout the forum, but haven't found any explanation as to what exactly is used for? (the POINTER data type, that is) Say, we create FC1, IN0 is of type POINTER, what can you do with IN0 inside FC1? I assume that somehow you can access the data that it points to, but how can this be done? Thanks for tips Boti

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6/8/2010 11:23 AM	Rate (0)
Aristotelis Posts: 147 Rating: (34)	Hi Perhaps this manual Programming with STEP 7 V5.4 may be of use to you, especially appendix A, where data types are discussed thoroughly. In general, pointers are just that: Pointers to some memory area. From manual: POINTER: references the address of a variable. A pointer contains an address instead of a value. When you supply a value to a formal parameter of the parameter type POINTER, you specify an address as the actual parameter. In STEP 7, you can specify a pointer in the pointer format or simply as an address (for example, M 50.0). Example of a pointer format for addressing the data beginning at M 50.0: P#M50.0 Try to read through the aforementioned manual, and if you still have any questions feel free to post them in the forum. Hope this helps
Aristotelis Posts: 147 Rating: (34)	Last edited by: Aristotelis at: 6/8/2010 11:29 AM Last edited by: Aristotelis at: 6/8/2010 11:28 AM Last edited by: Aristotelis at: 6/8/2010 11:28 AM
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6/8/2010 11:29 AM	Rate (0)
Saravana kumar Gold Member Joined: 2/6/2009 Last visit: 8/19/2024 Posts: 939 Rating: (118)	Dearjboti, Find the attached manual for the format of Any data type. I thing this will clear your doubt. Revert Back for any clarification. Attachment s7bashdB.pdf (2316 Downloads)
	_______________________________________________________________ Best Regards T.Saravana Kumar "All for the Best"
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6/8/2010 11:42 AM	Rate (0)
jboti Experienced Member Joined: 6/8/2007 Last visit: 9/9/2024 Posts: 53 Rating: (3)	Hi, The Programming with Step7 manual doesn't say anything more than the on-line help of Step7, which I already know. In the Appendix A.3.4.3. Using the Parameter Type POINTER there are some hints about reading the address of tags, but NOTHING about actally using a variable of POINTER type. Another thing: A.3.4.4. Block for Changing the Pointer (in the same manual) contains a sample FC, but this FC DOES NOT contain a parameter of POINTER type. Strange isn't it?

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6/8/2010 11:44 AM	Rate (0)
jboti Experienced Member Joined: 6/8/2007 Last visit: 9/9/2024 Posts: 53 Rating: (3)	Dear Saravana, I'm not interested in the ANY data type. I know it and use it extensively. All I'm interested in right now is the use of the POINTER data type. Boti

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6/8/2010 12:13 PM	Rate (0)
UMENCHO Diamond Member Joined: 3/21/2006 Last visit: 9/10/2024 Posts: 10228 Rating: (1181)	Hello Boti, Perhaps you "catch" the idea look at Syntax to use a Pointer declared in a variable table Best regards, Hristo Mihalev

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This contribution was helpful to 1 thankful Users jboti

6/8/2010 1:08 PM	Rate (0)
jboti Experienced Member Joined: 6/8/2007 Last visit: 9/9/2024 Posts: 53 Rating: (3)	UMENCHO Hello Boti, Perhaps you "catch" the idea look at Syntax to use a Pointer declared in a variable table Best regards, Hristo Mihalev Yepp, that's what I was looking for, thanks Hristo. Looks like my searching abilities are not too strong

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