4.4.3.5 Direct addresses
The following rules must be followed when using addresses for creating safety-oriented applications:
n No application of addresses directly in the program code. Each used address must be assigned to a vari-
able with “AT” in the declaration. In addition, we recommend identifying input/output variables through a
prefix and defining them together in a single variable list.
n The application of marker addresses (%M) should be limited to a minimum due to the error-proneness of
the allocation and the lack of purpose (memory for variables is allocated automatically).
n Multiple address allocation should be avoided due to obscure side effects. For word- and bit-wise access
a variable is defined for the word and accessed via bit access <variable>.<bit number>.
n No address declarations within programs, function blocks, functions and data structures
Configuration and programming
CoDeSys Safety programming guidelines > Language-specific programming guidelines
30.03.2017AC500-S214
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