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Unable to connect the output of block to the input of another block

Created by: chriswu at: 2/9/2013 1:11 AM (5 Replies)

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2/9/2013 1:11 AM	Rate (1)
chriswu Posts: 8 Rating: (1)	To simplify my question, I would like to use an example. What I want to do is to calculate A+B-C using FBD. So I added an "ADD" instruction and a "SUB" instruction into a network. A and B are assigned to the inputs of "ADD". However the output of "ADD" cannot be connected to IN1 of "SUB" no matter how I try. Am I missing something? The only way I can think of is separate the two instructions into two networks and create a temperary variable for the connection. But this takes extra time and the temperary variable is a unnecessary distraction in my opinion. Does someone know why I can't connect the output of ADD to the input of SUB?
chriswu Posts: 8 Rating: (1)
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2/9/2013 4:04 AM	Rate (0)
dchartier Grandmaster-Expert Joined: 9/27/2006 Last visit: 1/15/2025 Posts: 12328 Rating: (2699)	Hello chris; I am afraid that the temporary variable is the way to go. Look at the program example attached below, taken from the FBD manual: SIMATIC STEP7 V5.5 Function Block Diagram (FBD) for S7-300 and S7-400 Programming Hope this helps, Daniel Chartier Attachment FBD integer math.jpg (500 Downloads)

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This contribution was helpful to 1 thankful Users chriswu

2/9/2013 6:27 AM	Rate (0)
chriswu Posts: 8 Rating: (1)	HiDaniel, Thank you for answering my question. I appreciate it.
chriswu Posts: 8 Rating: (1)
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2/9/2013 12:49 PM	Rate (0)
dchartier Grandmaster-Expert Joined: 9/27/2006 Last visit: 1/15/2025 Posts: 12328 Rating: (2699)	Hello chris; The manual I proposed earlier was for Simatic Manager, I just saw that you posted in the TIA Portal section. In caseyou develop doubts about the answer based on the programmingplatform, here is the same example FBD code published in the TIA Portal manual: STEP 7 Professional V11.0 SP2 Hope this helps, Daniel Chartier Attachment FBD math TIA Portal.jpg (433 Downloads)

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This contribution was helpful to 1 thankful Users chriswu

2/9/2013 7:30 PM	Rate (0)
chriswu Posts: 8 Rating: (1)	Thanks,Daniel. I did notice the slight difference between the programming platforms but the basic ideas are the same.
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11/18/2021 7:40 PM
rezgd Regular Member Joined: 11/1/2021 Last visit: 9/3/2024 Posts: 11 Rating: (0)	Hi The example you shared is for LAD the main question is related to FBD not LAD. Regards

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