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Both CFC and Ladder Logic in s7300 PLC Project

Created by: Manoj Patel, Siemens , India at: 3/7/2013 1:20 PM (2 Replies)

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3/7/2013 1:20 PM	Rate (0)
Manoj Patel, Siem... Posts: 8 Rating: (0)	Hi, I have s7300 plc in My Project. Can i use both CFC and Ladder Logic in my Project? is there any limitation like CFC and Ladder can't used at a time...in Project.? Please confirm me... Thanks Manoj Patel
Manoj Patel, Siem... Posts: 8 Rating: (0)
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3/8/2013 10:33 AM	Rate (0)
dmertens Bronze Member Joined: 10/3/2007 Last visit: 3/15/2023 Posts: 188 Rating: (34)	Hi Manoj, That shouldn't be any problem, just write the FB/FCfunctions you need in ladder and then place them in a CFC where you want this function called. E.g. a CFC in OB1 or OB35. Only one caveat, make sure that if you are using global variables (flags, counters,...) that you can not use this block more than once. Normally multi-use FB's or FC's do not have global variables, the way to use variables that should be available in more places is through the use of connections in CFC or by using shared DB's. So rather than mix LAD and CFC, you should consider CFC a higher level in which you can call LAD/STL/FBD or SCL functions or function blocks. When you create a CFC, usually it get's created in OB35 but you can change the run sequence at any time, however make sure to never use library blocks that are time dependent (e.g. have an input with the attribute S7_sampletime like SAMPLE_T)in OB1 as these blocksuse the sample time of the cyclic OB tocalculate timers. If the time is not fixed thay will not work correctly. Hope this helps, David
	Last edited by: dmertens at: 3/8/2013 10:33 AM
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3/9/2013 11:57 AM	Rate (0)
Manoj Patel, Siem... Posts: 8 Rating: (0)	Hi, Thanks for Yr Reply... Now i got the Concepts... Thank you again for ur Help. Regard Manoj
Manoj Patel, Siem... Posts: 8 Rating: (0)
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