Allen-Bradley Logix5000 Reference Manual page 403

Description:
Arithmetic Status Flags:
Fault Conditions:
Execution:
Condition
Prescan
Rung-condition-in is false
Rockwell Automation Publication 1756-RM003N-EN-P - October 2011
Array (File)/Shift Instructions (BSL, BSR, FFL, FFU, LFL, LFU)
When enabled, the instruction unloads the uppermost bit of the specified bits to
the .UL bit, shifts the remaining bits one position left, and loads Source bit into
bit 0 of Array.
IMPORTANT
Not affected
A major fault will occur if
Length exceeds the size of Array's storage
area.
Relay Ladder Action
The .EN bit is cleared.
The .DN bit is cleared.
The .ER bit is cleared.
The .POS value is cleared.
The rung-condition-out is set to false.
The .EN bit is cleared.
The .DN bit is cleared.
The .ER bit is cleared.
The .POS value is cleared.
The rung-condition-out is set to false.
You must test and confirm that the instruction doesn't
change data that you don't want it to change.
The BSL instruction operates on contiguous memory. If an
Array is a member array, such as contained within a
structure, it is possible that the instruction could shift
beyond the Array's boundary into other members following
it. You must take care in choosing a length whereby this
does not happen.
Fault type
4
Chapter 9
Fault code
20
403