Chapter 4. Ladder Diagram (LD) Programming
GFK-2950C
February 2018
201
4.11
Program Flow Functions
The program flow functions limit program execution or change the way the CPU executes the
application program.
Function
Mnemonic Description
Argument
Present
ARG_PRES Determines whether an input or output parameter value was present when the
function block instance of the parameter was invoked. For example, a parameter
can be optional (pass by value).
Call
CALL
Causes program execution to go to a specified block.
Comment
COMMENT Places a text explanation in the program.
End Master
Control Relay
ENDMCRN Nested End Master Control Relay. Indicates that the subsequent logic is to be
executed with normal power flow.
End of Logic END
Provides an unconditional end of logic. The program executes from the first rung to
the last rung or the END instruction, whichever is encountered first.
Jump
JUMPN
Nested jump. Causes program execution to jump to a specified location indicated
by a LABELN. JUMPN/LABELN pairs can be nested within one another. Multiple
JUMPNs can share the same LABELN.
Label
LABELN
Nested label. Specifies the target location of a JUMPN instruction.
Master
Control Relay
MCRN
Nested Master Control Relay. Causes all rungs between the MCR and its
subsequent ENDMCRN to be executed without power flow. Up to MCRN/ENDMCRN
pairs can be nested within one another. All the MCRNs share the same ENDMCRN.
Wires
H_WIRE
Horizontally connects elements of a line of LD logic, to complete the power flow.
V_WIRE
Vertically connects elements of a line of LD logic, to complete the power flow.
Summary of Contents for PACSystems RSTi-EP
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