Rockwell Automation AutoMax Enhanced Ladder Language Reference Manual - Manual (Page 206)

10Ć4
How Array Instructions Execute
The array instructions execute following this sequence of events:
D The array instructions execute when the enable bit for the instruction first transitions
from false to true. If the enable bit is set false before the array operation is
completed, the operation is canceled.
D The instruction's input and output control parameters are latched.
Array variables are not latched. Therefore, be aware that the values may be changed
if another program is writing into some or all of the array elements. This also can
occur when the array operation is to complete in a single scan and a higher priority
program or a program from another Processor is writing data to the array.
However, if a single array element or variable (length=1) is used as a parameter, it is
latched to ensure that the value remains fixed even though the operation may occur
over multiple scans.
D Once the control variables are latched and limit checking on the data is complete,
the instruction performs the programmed array operation.
The instruction immediately performs the operation when you specify a 0 for the
Elems/Scan input. If this input is not 0, the actual array operation begins on the
second scan.
D When the instruction finishes operating on the last element within the array, the done
(DN) bit becomes true.
Tip
If the instruction's operation is distributed among two or more program scans, you can
determine how far into the array operation that the instruction is by monitoring Index.
The Index output parameter indicates the last element that was operated on during the
last scan.