Rockwell Automation 1761 MicroLogix 1000 Programmable Controllers - Manual (Page 175)

Using Data Handling Instructions
9–27
LFL Instruction
When rung conditions change from false-to-true, the controller sets the LFL enable
bit (EN). This loads the contents of the Source, N7:10, into the stack element
indicated by the Position number, 9. The position value then increments.
The LFL instruction loads an element at each false-to-true transition of the rung,
until the stack is filled (34 elements). The controller sets the done bit (DN),
inhibiting further loading.
LFU Instruction
When rung conditions change from false-to-true, the controller sets the LFU enable
bit (EU). This unloads data from the last element loaded into the stack (at the
position value minus 1), placing it in the Destination, N7:11. The position value
then decrements.
The LFU instruction unloads one element at each false-to-true transition of the rung,
until the stack is empty. The controller then sets the empty bit (EM).
Programming
Execution Times
(
µ
sec) when:
True False
61.13 33.67
64.20
Execution Times
(
µ
sec) when:
True False
35.08