Omron CX-PROGRAMMER 5.0-FUNCTION BLOCK OPERATION Operation Manual page 14

Application Precautions
• Values are passed in a batch from the input parameters to the input vari-
ables before algorithm execution (not at the same time as the instructions
in the algorithm are executed). Therefore, to pass the value from a
parameter to an input variable when an instruction in the function block
algorithm is executed, use an internal variable or external variable instead
of an input variable. The same applies to the timing for writing values to
the parameters from output variables.
• Always use internal variables with AT settings in the following cases.
• The addresses allocated to Basic I/O Units, Special I/O Units, and
CPU Bus Units cannot be registered to global symbols, and these vari-
ables cannot be specified as external variables (e.g., the data set for
global variables may not be stable).
• Use internal variables when Auxiliary Area bits other than those pre-
registered to external variables are registered to global symbols and
these variables are not specified as external variables.
• Use internal variables when specifying PLC addresses for another
node on the network: For example, the first destination word at the re-
mote node for SEND(090) and the first source word at the remote
node for RECV(098).
• Use internal variables when the first or last of multiple words is speci-
fied by an instruction operand and the operand cannot be specified as
an internal array variable (e.g., the number of array elements cannot
be specified).
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