These guidelines will help you avoid common programming errors and write programs that run faster and are easier to maintain. The PPCL guidelines are as follows:

  • A program defined in one automation station is not recommended to be used to control objects in a different automation station.
  • Loop statements should not be closed across a network.
  • Time-based commands (for example, LOOP, SAMPLE, TOD, WAIT, etc.) should be evaluated through every pass of the program for proper operation.
  • If program execution is interrupted (for example, during a power failure), the system always resumes processing at the first line of the program. Therefore, the first line of the program should be executed through every pass of the program.
    • Routing commands (such as GOTO) should transfer program control to a sequentially higher line number. This practice prevents programs from being caught in endless loops.
  • On PXC.A controllers, jumping backwards in the program signals an end to the program cycle and restarts the cycle time calculations.