Allen-Bradley Logix5000 Reference Manual page 469

Program Control Instructions (JMP, LBL, JSR, RET, SBR, JXR, TND, MCR, UID, UIE, AFI, NOP, EOT, SFP, SFR, EVENT) Chapter 11
Example:
When the first MCR instruction is enabled (input_1, input_2, and input_3 are
set), the controller executes the rungs in the MCR zone (between the two MCR
instructions) and sets or clears outputs, depending on input conditions.
When the first MCR instruction is disabled (input_1, input_2, and input_3 are
not all set), the controller executes the rungs in the MCR zone (between the two
MCR instructions) and the rung-condition-in goes false for all the rungs in the
MCR zone, regardless of input conditions.
Rockwell Automation Publication 1756-RM003N-EN-P - October 2011 469