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+1  Q: 

Pointers and online change in TwinCAT and CoDeSys

Are pointers safe against online change of running PLC program in TwinCAT 2.10 and in CoDeSys 2.3 on which the first one is based? What happens if memory block gets reallocated as part of online program change and there are pointers pointing to that memory block?

+2  A: 

ADR (Address Operator) description in TwinCAT's help says:

Attention: After an Online Change there might be changes concerning the data on certain addresses. Please regard this in case of using pointers on addresses.

It looks to me like pointers cannot be stored permanently if someone pretends to use online modification of the program. Otherwise if pointers are stored (for example as a binding between some data structures) online change should be avoided.

Taras Boyko  2010-01-04 17:01:42

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