11/24/2009 12:03 AM | |
Joined: 10/7/2005 Last visit: 9/24/2024 Posts: 3022 Rating: (1054)
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Hello franbel have a look at the link below, I hope it answersyour question: Significance and use of the BR bit |
Cheers |
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11/24/2009 8:48 AM | |
Joined: 10/7/2005 Last visit: 9/24/2024 Posts: 3022 Rating: (1054)
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Hello again franbel not too sure ifI understand your question correctly. If you"make use" of the EN when you callyour FC, it means you are doing a conditional (LAD or FBD based) call of the FC (be it based on the status of a bit or comparator or whatever else you "construct" and link it to the EN). The "EN" of an FC is of course a "cosmetic" thing for LAD/FBD display purposes and it is the RLO-->BR bit related jump behind the (STL) scenes that make it work. Nonetheless, there are as such only two possibilities: 1.) The FC is NOT being called 2.) The FC is being called If 1.) is the case, there is no point in trying to "use" the BR bit further inside the FC (since the logic inside the FC is not executed). If 2.) is the case, your logic inside the FC will be executed which means the BR bithad to be on (i.e. checking the BR bit in your FC would bea foregone conclusion). A third case would be if you call the FC unconditionally (i.e. the "EN" is linked directly to the "power rail" on the left hand side if displayed in LADDER). You could now check the BR bit inside teh FC, but it would again be meaningless since it would have the status of whatever last condition/command had set it to. Having said all of the above, you do have "contacts' in the"Status Bits" section of your Ladder (or FBD) programming elements to check the status of the BR bit, so you can in general question its status. I hope this helps |
Cheers |
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