Installation manual

Publication 1747-RM001G-EN-P - November 2008
6-6 Program Flow Instructions
Master Control Reset (MCR)
Use MCR instructions in pairs to create program zones that turn off all the
non-retentive outputs in the zone. Rungs within the MCR zone are still
scanned, but scan time is reduced due to the false state of non-retentive
outputs.
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.
• always place the MCR instruction as the last instruction in a rung.
Processor Operation
Do not jump (JMP) into an MCR zone. Instructions that are programmed
within the MCR zone starting at the LBL instruction and ending at the END
MCR instruction are always evaluated as though the MCR zone is true,
regardless of the true state of the Start MCR instruction. If the zone is false,
jumping into it activates the zone from the LBL to the end of the zone.
(MCR)
Fixed SLC
5/01
SLC
5/02
SLC
5/03
SLC
5/04
SLC
5/05
• •••••
Table 6.3 Controller Function
If the MCR Rung
that Starts the
Zone is
Then the Controller
True Executes the rungs in the MCR zone based on each rung’s
individual input condition (as if the zone did not exist).
False Resets all non-retentive output instructions in the MCR zone
regardless of each rung’s individual input conditions.