Introduction

Chapter 11 Program Control Instructions (JMP, LBL, JSR, RET, SBR, JXR, TND, MCR, UID, UIE, AFI, NOP, EOT, SFP, SFR, EVENT)

Master Control Reset (MCR)

The MCR instruction, used in pairs, creates a program zone that can disable all rungs within the MCR instructions.

Operands:

Relay Ladder

none

Description:

When the MCR zone is enabled, the rungs in the MCR zone are scanned for normal true or false conditions. When disabled, the controller still scans rungs within an MCR zone, but scan time is reduced because non-retentive outputs in the zone are disabled. The rung-condition-in is false for all the instructions inside of the disabled MCR zone.

When you program an MCR zone, 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 the zone activates the zone from the point to which you jumped to the end of the zone.

•

If an MCR zone continues to the end of the routine, you do not have to program an MCR instruction to end the zone.

The MCR instruction is not a substitute for a hard-wired master control relay that provides emergency-stop capability. You should still install a hard-wired master control relay to provide emergency I/O power shutdown.

ATTENTION

Do not overlap or nest MCR zones. Each MCR zone must be separate and complete. If they overlap or nest, unpredictable machine operation could occur with possible damage to equipment or injury to personnel.

Place critical operations outside the MCR zone. If you start instructions such as timers in a MCR zone, instruction execution stops when the zone is disabled and the timer is cleared.

Arithmetic Status Flags:

not affected

Fault Conditions:

none

452

Publication 1756-RM003K-EN-P - July 2008

Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com

Program Control Instructions (JMP, LBL, JSR, RET, SBR, JXR, TND, MCR, UID, UIE, AFI, NOP, EOT, SFP, SFR, EVENT) Chapter 11

Condition

prescan rung-condition-in is false rung-condition-in is true postscan

Execution:

Relay Ladder Action

The rung-condition-out is set to false.

The rung-condition-out is set to false.

The instructions in the zone are scanned, but the rung-condition-in is false and non-retentive outputs in the zone are disabled.

The rung-condition-out is set to true.

The instructions in the zone are scanned normally.

The rung-condition-out is set to false.

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.

Publication 1756-RM003K-EN-P - July 2008

Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com

453