CH 12: PLC SubRoutine Functions

What is a key feature of PLC ladder logic diagrams that incorporate subroutines?

• They use only one subroutine

• They incorporate one or more subroutines

• They do not use any subroutines

• They are only used for input devices

What determines the specific subroutine to be executed in a PLC program scan?

• The time of day

• The state of an input device or result of a compare instruction

• The temperature

• The user’s preference

Where is the main ladder logic diagram, or main file, located?

• Program file number one

• Program file number two

• Program file number three

• Program file number four

What is the advantage of writing programs with several modules or subroutines?

• They are more complex and harder to debug.

• They can be tested individually to ensure accuracy.

• They require more memory to run.

• They cannot be called from the main program.

What does the program counter hold?

• The address of the current instruction

• The address of the next instruction

• The address of the previous instruction

• The address of the first instruction

Which of the following is held in the stack created by the PLC processor?

• Data register

• Program counter

• Memory address

• Instruction set

What happens after the processor creates a stack due to a call instruction?

• It halts the program

• It starts executing instructions in a subroutine module

• It clears the memory

• It resets the registers

What is the main topic of the diagram?

• Ladder Logic Diagram Using Subroutines

• Circuit Design with Resistors

• Flowchart for Software Development

• Electrical Wiring Diagram

What does the label "I:0" represent in the diagram?

• Input address

• Output address

• Voltage level

• Current level

What instruction must be at the beginning of a subroutine file to indicate it is a subroutine?

• RET instruction

• SBR instruction

• END instruction

• JMP instruction