Relay Ladder - Allen-Bradley Logix5000 Reference Manual

Program Control Instructions (JMP, LBL, JSR, RET, SBR, JXR, TND, MCR, UID, UIE, AFI, NOP, EOT, SFP, SFR, EVENT)
Description:
Arithmetic Status Flags:
Fault Conditions:
Execution:
Condition
Prescan
Rung-condition-in is false
Rung-condition-in is true
EnableIn is set
Instruction execution
Postscan
When the SFR instruction is enabled:
· In the specified SFC routine, all stored actions stop executing (reset).
· The SFC begins executing at the specified step.
If the target step is 0, the chart will be reset to its initial step.
The Logix implementation of the SFR instruction differs from that in a PLC-5
controller. In the PLC-5 controller, the SFR executed when the rung condition
was true. After reset, the SFC would remain paused until the rung containing the
SFR became false. This allowed the execution following a reset to be delayed.
This pause/un-pause feature of the PLC-5 SFR instruction was decoupled from
the rung condition and moved into the SFP instruction.
Not affected
A major fault will occur if
Routine type is not an SFC routine
Specified target step does not exist in the
SFC routine
Relay Ladder Action
The rung-condition-out is set to false.
The rung-condition-out is set to false.
The instruction executes.
The rung-condition-out is set to true.
N/A
The instruction resets the specified SFC routine.
The rung-condition-out is set to false.
Example:
If a specific condition occurs (shutdown is set), restart the SFC at step initialize.

Relay Ladder

Rockwell Automation Publication 1756-RM003N-EN-P - October 2011
Fault type
4
4
Structured Text Action
No action taken.
N/A
N/A
EnableIn is always set.
The instruction executes.
The instruction resets the specified SFC routine.
No action taken.
Chapter 11
Fault code
85
89
479