Control Functions Master Control Relay (Mcr) / End Mcr - GE VersaMax PLC User Manual

142 GFK-1503E
For public disclosure
10.2.4 Control Functions Master Control Relay (MCR)
/ End MCR
All rungs between an active Master Control Relay (MCRN) and its corresponding End
Master Control Relay (ENDMCRN) function are executed without power flow to coils.
The ENDMCRN associated with the Master Control Relay is used to resume normal
program execution. Unlike Jump functions, Master Control Relays can only move
forward; the ENDMCRN must appear after its corresponding Master Control Relay
instruction in a program.
10.2.4.1 Nested MCR
A Nested Master Control Relay function can be nested completely within another
MCRN/ENDMCRN pair.
There can be multiple Master Control Relay functions with a single ENDMCRN.
The Master Control Relay function has an enable input and a name. This name is used
again with the ENDMCRN. The Master Control Relay has no outputs; there can be
nothing after it in a rung.
enable
MCR
With a Master Control Relay, function blocks within the scope of the Master Control
Relay are executed without power flow, and coils are turned off.
The ENDMCRN function must be tied to power rail; there can be no logic before it in the
rung. The name of the ENDMCRN associates it with the corresponding Master Control
Relay(s). The ENDMCRN function has no outputs; there can be nothing after it in a rung.
10.2.4.2 Example Master Control Relay and ENDMCRN
Functions
In the example, when %I0002 is ON, the Master Control Relay is enabled. When the
Master Control Relay is enabled–even if %I0001 is ON–the Addition function block is
executed without power flow (i.e., it does not add 1 to %R0001), and %Q0001 is turned
OFF.
If %I0003 and %I0004 are ON, %Q0003 is turned OFF and %Q0004 remains ON.
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