Minimize Instruction Operation

  • Make the size of the following as small as needed for the application:
    • Data arrays/structures/UDTs
    • Add-On Instructions
    • FBD routines
  • For FBD routines, use Function Block functions when possible. Function Block functions do not have backing tag structures and reduce the amount of data that requires crossloading.
  • BSR, BSL, FAL, FBC, DDT, SRT, and FFU instructions
    When referencing controller-scoped tags in a lower or same priority task, partial updates can be crossloaded to the secondary as part of the other task's sync point. If a switchover occurs, the instruction could have incorrect data. Use UID/UIE pairs around the instruction or use program-scoped tags instead.
  • When performing MSG reads, the MSG backing tag and the data tag should be at the same scope so that they are tracked together.
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