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2.3.4 Stand-by type program
(1) Definition
Stand-by type program is executed only when its execution is requested.
This type of program can be changed to any desired execution type by a sequence program instruction.
(2) Application
(a) Program library
Stand-by type program is used as a program library, a collection of subroutine programs and/or interrupt
programs, and managed separately from a main routine program.
Multiple subroutine programs and/or interrupt programs can be created and managed in a single stand-by type
program.
(b) Program type change
Stand-by type program is used to create and store programs available in all systems. Only required programs
will be executed.
For example, a program preset as a stand-by ("Wait") type program in the PLC parameter dialog box can be
changed to a scan execution type program and executed in the sequence program.
Figure 2.33 Program library using a stand-by type program
P100
I0
P100
I0
Scan execution type program
Scan execution type program
Stand-by type program
Main routine
program
Main routine
program
Subroutine
program
Interrupt
program
Subroutine
program
Interrupt
program