3/7/2011 11:53 PM | |
Joined: 5/4/2009 Last visit: 5/28/2024 Posts: 914 Rating: (40) |
Dear hdhosseini, I have another question if you dont mind, is it ligal to use DB58 variables within OB1 or is it restricted within FB58? Regards. Tomy. Splitted from FB58 & FB59. |
Last edited by: O_Moderator at: 3/9/2011 9:26 AMnew subject after splitting Aim Higher |
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3/8/2011 1:07 AM | |
Joined: 10/7/2005 Last visit: 9/25/2024 Posts: 3022 Rating: (1054)
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Hello Tomy Master An IDB (Instance Data Block) "belongs" to an FB and act as its "memory". Unlike "Global DB's" you can not edit/change the structure of an IDB directly (its structure is defined by the FB variable declarations) and you would (should in an ideal world)NOT use elements of an IDB outside the FB to which it belongs. Having said that, an IDB is still just a DBand it is permissible (or "legal") to write/read to/from it outside of the FB to which it belongs (you can even link them to an HMI if need be). As Siemens have createda very lean interface forFB58/59 which does not include variables such as Gain, TI,etc. etc. youdon't really have a choiceand must write to these from outside the FB if you want to be able to chance/preset them via the program (all thethese IDB "hidden" variables are fortunately all listed andexplained as "internal parameters" under the F1 contextsensitive help of the FB's). I hope this helps |
Cheers |
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