Installation manual

Publication 1747-RM001G-EN-P - November 2008
Program Flow Instructions 6-7
Temporary End (TND)
This instruction, when its rung is true, stops the processor from scanning the
rest of the program file, updates the I/O, and resumes scanning at rung 0 of
the main program (file 2). If this instruction’s rung is false, the processor
continues the scan until the next TND instruction or the END statement. Use
this instruction to progressively debug a program, or conditionally omit the
balance of your current program file or subroutines.
ATTENTION
If you start instructions such as timers or counters in
an MCR zone, instruction operation ceases when the
zone is disabled. Re-program critical operations
outside the zone if necessary.
The TOF timer activates when placed inside of a false
MCR zone.
The MCR instruction is not a substitute for a
hard-wired master control relay. We recommend that
your programmable controller system include a
hard-wired master control relay and emergency stop
switches to provide I/O power shut down.
Emergency stop switches can be monitored but
should not be controlled by the ladder program. Wire
these devices as described in the installation manual.
SLC 5/03 and higher processors - When online and an
unmatched MCR instruction exists in your program,
the END instruction acts as the second unconditional
MCR instruction and all of the rungs following the
first MCR instruction execute via the current MCR
instruction state.
You can save the program while online if unmatched
MCR instructions exist. However, if you are offline
and unmatched MCR instructions exist, an error will
occur.
(TND)
Output Instruction
Fixed SLC
5/01
SLC
5/02
SLC
5/03
SLC
5/04
SLC
5/05
• •••••
TIP
If you use this instruction inside a nested subroutine,
execution of all nested subroutines is terminated.