Program a Function Block Diagram
Rockwell Automation Publication 1756-PM009G-EN-P - February 2018 13
For a: Specify:
Element of a two dimension array
tag_name[x,y]
Element of a three dimension array
tag_name[x,y,z]
Element of an array within a structure
tag_name.member_name[x]
Member of an element of an array
tag_name[x,y,z].member_name
where:
x is the location of the element in the first dimension.
y is the location of the element in the second dimension.
z is the location of the element in the third dimension.
For a structure within a structure, add an additional member_name.
Define execution order (flow of data) by wiring elements together and
indicating any input (feedback) wires, if necessary. The location of a block
does not affect the order in which the blocks execute.
If you use an IREF to specify input data for a function block instruction, the
data in that IREF is latched for the scan of the function block routine. The
IREF latches data from program-scoped and controller-scoped tags. The
controller updates all IREF data at the beginning of each scan as shown in
this diagram.
In this example, the value of tagA is stored at the beginning of the execution
of the routine. The stored value is used when Block_01 executes. The same
stored value is also used when Block_02 executes. If the value of tagA
execution
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