Publication 1762-RM001C-EN-P
14-8 File Instructions
FFL - First In, First Out
(FIFO) Load
Instruction Type: output
On a false-to-true rung transition, the FFL instruction loads words or long
words into a user-created file called a FIFO stack. This instruction’s
counterpart, FIFO unload (FFU), is paired with a given FFL instruction to
remove elements from the FIFO stack. Instruction parameters have been
programmed in the FFL - FFU instruction pair shown below.
EN
DN
EM
FFL
FIFO Load
Source N7:0
FIFO #N7:1
Control R6:0
Length 1<
Position 0<
FFL
Table 14.10 Execution Time for the FFL Instruction
Controller Data Size When Rung Is:
True False
MicroLogix 1200 word 11.3
µ
s 11.1
µ
s
long word 11.7
µ
s 11.2
µ
s
MicroLogix 1500 word 10.0
µ
s9.8
µ
s
long word 10.9
µ
s9.7
µ
s
(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)
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
Loading and Unloading of Stack #N7:12
FFL and FFU Instruction Pair
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