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execution times load/transfer in multiple instance

Created by: Marko Bursic at: 11/14/2011 6:05 PM (2 Replies)

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11/14/2011 6:05 PM	Rate (0)
Marko Bursic Platinum Member Joined: 9/8/2009 Last visit: 3/15/2023 Posts: 1410 Rating: (148)	Hi, I have noticed that for example if I use afunction block and then accessstatic or output variables of instance data block from OB, FC or FB is time consuming: each time I access a vaiable like: A DB1.DBX0.0 =DB1.DBX0.1 the CPUperforms an OPN command on each access, while the same thing can do this: OPN DB1 A DBX0.0 =DBX0.1 In LAD programming will always compile an access of data block with symboli***resentation like in first examle, so each access cpu performsOPNDBx command. Now the question is: what if I put all FBs as multiple instances into one FBand then access them - I should stay into the same data block, so isOPN DBx avoided using multiple instances?

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11/18/2011 12:24 PM	Rate (0)
Cicero Gold Member Joined: 10/10/2005 Last visit: 3/16/2023 Posts: 1909 Rating: (132)	Hello, please see the FAQ in the internet and perhaps it could be mainful for you. http://support.automation.siemens.com/WW/view/de/10810851 With best regards Cicero

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11/18/2011 2:49 PM	Rate (0)
Marko Bursic Platinum Member Joined: 9/8/2009 Last visit: 3/15/2023 Posts: 1410 Rating: (148)	Thank you for your reply, but my question was related right the article that you proposed. As you may see with symbolic addressing a plc executes two operations OPN and Load each access. When I switch off symolic addressing in editor in a block that uses multiple instances (groups of same devices, ..motors,cylinders,pumps..) the sybolic name remains. I assume that when using multiple instances you remain within same data block, so there is no need to execute OPN commands continuosly.

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