Page 271 - Programmable Logic Controllers, Fifth Edition - Mobile version
P. 271
12
Sequencer and Shift
Register Instructions
Image Courtesy Banner Engineering Corp.
Chapter Objectives
This chapter explains how the PLC sequencer After completing this chapter, you will be able to:
and shift register functions operate and how • Identify and describe the various forms of mechanical
they can be applied to control problems. The se- sequencers and explain the basic operation of each
quencer instruction evolved from the mechanical • Interpret and explain information associated with PLC
drum switch, and it can handle complex sequenc- sequencer output, compare, and load instructions
ing control problems more easily than does the • Compare the operation of an event-driven and a time-
drum switch. Shift registers are often used to driven sequencer
track parts on automated manufacturing lines by • Describe the operation of bit and word shift registers
shifting either status or values through data files. • Interpret and develop programs that use shift registers
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