Publication 1766-RM001A-EN-P - October 2008
Program Control Instructions
301
While the rung state of the first MCR instruction is true, execution
proceeds as if the zone were not present. When the rung state of the first
MCR instruction is false, the ladder logic within the MCR zone is executed
as if the rung is false. All non-retentive outputs within the MCR zone are
reset.
MCR zones let you enable or inhibit segments of your program, such as
for recipe applications.
When you program MCR instructions, note that:
•
You must end the zone with an unconditional MCR instruction.
•
You cannot nest one MCR zone within another.
•
Do not jump into an MCR zone. If the zone is false, jumping into it
activates the zone.
TIP
The MCR instruction is not a substitute for a hard-wired master control
relay that provides emergency stop capability. You still must install a
hard-wired master control relay to provide emergency I/O power shutdown.
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.
efesotomasyon.com - Allen Bradley,Rockwell,plc,servo,drive
