Rievtech xLogic ELC Series User Manual page 278

Variable AI:
You can't change the value of variable AI.
Variable AQ:
When the input pin of analog output block AQ is not connected,you can change the value of variable AQ.
If the input pin of analog output block AQ is already connected with other blocks,you can't change the
value of variable AQ anymore.
Variable F:
When the input pin of digital flag variable F is not connected,you can change the status of variable F.
If the input pin of digital flag block F is already connected with other blocks,you can't change the status
of variable F anymore.
Variable AF:
When the input pin of analog flag block AF is not connected,you can change the value of variable AF
If the input pin of analog flag block AF is already connected with other blocks,you can't change the value
of variable AF anymore.
Variable HEG:
Cannot be set, only can be read.
Variable M:
You can't change the status of variable M, it only can be read.
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