Page 271 - Programmable Logic Controllers, Fifth Edition Mobile 2
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
252
pet73842_ch12_252-280.indd 252 03/11/15 7:18 PM
