Publication 1766-RM001A-EN-P - October 2008
306 Input and Output Instructions
Addressing Modes and File Types can be used as shown below:
REF- I/O Refresh
Instruction Type: output
The REF instruction is used to interrupt the program scan to execute the
I/O scan and service communication portions of the operating cycle for
all communication channels. This includes: write outputs, service
communications (all communication channels, communications toggle
functionality, and comms housekeeping), and read inputs.
The REF instruction has no programming parameters. When it is evaluated
as true, the program scan is interrupted to execute the I/O scan and
service communication portions of the operating cycle. The scan then
resumes at the instruction following the REF instruction.
The REF instruction cannot be executed from an STI subroutine, HSC
subroutine, EII subroutine, or a user fault subroutine.
IOM Instruction Valid Addressing Modes and File Types
For definitions of the terms used in this table see Using the Instruction Descriptions on page 92.
Parameter
Data Files Function Files
CS - Comms
IOS - I/O
DLS - Data Log
Address
Mode
Address Level
O
I
S
B
T, C, R
N
F
ST
L
MG, PD
RI/RIX
PLS
RTC
HSC
PTOX, PWMX
STI
EII
BHI
MMI
LCD
Immediate
Direct
Indirect
Bit
Word
Long Word
Element
Slot • • • •
Mask • • • • •
• • ••
Length
•
REF
Execution Time for the REF Instruction
Controller When Rung Is:
True False
MicroLogix 1400 See MicroLogix 1400 Scan Time
Calculation on page 550
0.1490 µs
TIP
Using an REF instruction may result in input data changing in the middle of
a program scan. This condition needs to be evaluated when using the REF
instruction.
ATTENTION
The watchdog and scan timers are reset when executing the REF
instruction. You must insure that the REF instruction is not placed inside a
non-terminating program loop. Do not place the REF instruction inside a
program loop unless the program is thoroughly analyzed.
efesotomasyon.com - Allen Bradley,Rockwell,plc,servo,drive
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