428 Rockwell Automation Publication 1756-RM003N-EN-P - October 2011
Chapter 9 Array (File)/Shift Instructions (BSL, BSR, FFL, FFU, LFL, LFU)
LIFO Unload (LFU)
The LFU instruction unloads the value at .POS of the LIFO and stores 0 in that
location.
Operands:
Relay Ladder
If you use a user-defined structure as the data type for the LIFO or Destination
operand, use the same structure for both operands.
Operand Type Format Description
LIFO SINT
INT
DINT
REAL
string
structure
Array tag LIFO to modify
Specify the first element of the LIFO
Do not use CONTROL.POS in the subscript
Destination SINT
INT
DINT
REAL
string
structure
Tag Value that exits the LIFO
The Destination value converts to the data type of the Destination tag. A
smaller integer converts to a larger integer by sign-extension.
Control CONTROL Tag Control structure for the operation
Typically use the same CONTROL as the
associated LFL
Length DINT Immediate Maximum number of elements the LIFO can
hold at one time
Position DINT Immediate Next location in the LIFO where the
instruction unloads data
Initial value is typically 0
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