Page 203 - Programmable Logic Controllers, Fifth Edition - Mobile version

9

Program Control

Instructions

Inputs Ladder logic program Outputs

L1 PB PL1 L2
1
PB PL1
Switch Q2:0
2 JMP
Switch PL2
PB PL2
3 PL3

Q2:0 PB PL3
4 LBL

Chapter Objectives

The program control instructions covered in this After completing this chapter, you will be able to:
chapter are used to alter the program scan from • State the purpose of program control instructions
its normal sequence. The use of program con- • Describe the operation of the master control reset
trol instructions can shorten the time required to instruction and develop an elementary program
complete a program scan. Portions of the pro- illustrating its use
gram not being utilized at any particular time can • Describe the operation of the jump instruction and the
be jumped over, and outputs in specific zones in label instruction
the program can be left in their desired states. • Explain the function of subroutines
Typical industrial program control applications • Describe the immediate input and output instructions
are explained. function
• Describe the forcing capability of the PLC
• Describe safety considerations built into PLCs and
programmed into a PLC installation
• Explain the differences between standard and safety PLCs
• Describe the function of the selectable timed interrupt
and fault routine files
• Explain how the temporary end instruction can be used
to troubleshoot a program

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