10/10/2007 6:45 AM | |
Joined: 5/19/2006 Last visit: 8/15/2024 Posts: 548 Rating:
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From STEP7 STL Help / Parameter Transfer: "The parameters of a block are transferred as a value ?? Well, how exactly the parameters are transferred to FC seems to be hidden from the user by STL editor. [code] After removing STEP7 CALL construct the plain STL (phase 1) will be: [code] So far so good. [code] STEP7 STL editor inject JU_LABEL instruction after every CALL/UC to bypass & wrap the FC IN, OUT andIN_OUT parameter pointersstructure. Attached is a screen-shot with above example where FC1 (rung 2) reads OB1 instructions after the CALL (OB1 rung 2). AttachmentParamFC.zip (317 Downloads) |
Last edited by: Dec at: 10.10.2007 08:00Bottom line the example in purpose shows a common programming error when the programmer have changed the called block interface (add more parameters) but have not update the calling block to reflect the changes. Last edited by: Dec at: 10.10.2007 07:47Last edited by: Dec at: 10.10.2007 07:27 |
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2 thankful Users |
12/17/2007 1:17 PM | |
Posts: 2348 Rating:
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Perfect topic, Dec. I finallygottimetomakeacloserlookonit-it'sveryinteresting. Havingsomethoughtshowtoimplementcodeprotection,basedonthisprinciple. |
12/26/2007 7:51 PM | |
Joined: 5/19/2006 Last visit: 8/15/2024 Posts: 548 Rating:
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Hi Late, For FBs all IN/OUT/IN_OUT are exchanged via DI instance DB. Dec |
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