Installation manual

Publication 1747-RM001G-EN-P - November 2008
Data Handling Instructions 5-27
FFL Instruction Operation
When rung conditions change from false-to-true, the FFL enable bit (EN) is
set. 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 FFL instruction loads an element at each false-to-true transition of the
rung, until the stack is filled (34 elements). The processor then sets the done
bit (DN), inhibiting further loading.
FFU Instruction Operation
When rung conditions change from false-to-true, the FFU enable bit (EU) is
set. This unloads the contents of the element at stack position 0 into the
destination, N7:11. All data in the stack is shifted one element toward position
zero, and the highest numbered element is zeroed. The position value then
decrements.
The FFU instruction unloads an element at each false-to-true transition of the
rung, until the stack is empty. The processor then sets the empty bit (EM).
Table 5.19 Instruction Function
Destination Position
N7:11 N7:12 0
N7:13 1
FFU instruction
unloads data from
stack #N7:12 at
position 0, N7:12
N7:14 2
3
4
5 34 words are allocated for FIFO
stack starting at N7:12, ending
at N7:45
6
7
Source 8
N7:10 9
FFL instruction loads
data into stack
#N7:12 at the next
available position, 9
in this case.
N7:45 33
(EU)
(EM)
(DN)
FFL
FIFO LOAD
Source N7:10
FIFO #N7:12
Control R6:0
Length 34
Position 9
FFU
FIFO UNLOAD
FIFO #N7:12
Dest N7:11
Control R6:0
Length 34
Position 9
(EN)
(DN)
(EM)