Page 296 - Programmable Logic Controllers, Fifth Edition - Mobile version

CHAPTER 12 REVIEW QUESTIONS

1. Describe the operation of a drum switch.
1. Describe the operation of a drum switch. 12. What is the primary application in which an SQL
2. What type of operations are sequencers most
2. What type of operations are sequencers most instruction is used?
suitable for?
suitable for? 13. Explain the function of a sequencer load
3. Why are PLC sequencers easier to program than instruction.
3. Why are PLC sequencers easier to program than
PLC discrete outputs? 14. How does a bit shift register manipulate individual
PLC discrete outputs?
4. Answer the following with regard to an SLC 500
4. Answer the following with regard to an SLC 500 bits?
PLC sequencer output instruction: 15. List four common applications for bit shift
PLC sequencer output instruction:
a. Where is the information for each sequencer
a. Where is the information for each sequencer registers.
step entered? 16. When using a sensor as the input to the bit address
step entered?
b. What is the function of the output word?
b. What is the function of the output word? of a BSL instruction, what is its function?
c. Explain the transfer of data that occurs as the 17. Compare the operation of the BSL and BSR bit
c. Explain the transfer of data that occurs as the
sequencer is advanced through its various steps. shift instructions.
sequencer is advanced through its various steps.
5. What is the function of the file of a sequencer?
5. What is the function of the file of a sequencer? 18. A bit shift register is said to operate in a synchro-
6. What is the function of the mask in the sequencer
6. What is the function of the mask in the sequencer nous manner. Explain what this means.
instruction? 19. What is the function of the unload bit in a BSL
instruction?
7. What is the relationship between the length and the
7. What is the relationship between the length and the instruction?
position in a sequencer instruction?
position in a sequencer instruction? 20. What is the function of the unload bit in a BSR
8. What output and step programming limits may be
8. What output and step programming limits may be instruction?
placed on sequencer instructions?
placed on sequencer instructions? 21. A first in, first out word shift register operates in an
9. Sequencer instructions are usually retentive. asynchronous manner. Explain what this means.
9. Sequencer instructions are usually retentive.
Explain what this means.
Explain what this means. 22. Why are both FFL and FFU instructions needed to
10. Compare the operation of an event-driven and a perform a FIFO function?
10. Compare the operation of an event-driven and a
time-driven sequencer.
time-driven sequencer. 23. Compare the operation of a FIFO register and a
11. Explain the function of a sequencer compare
11. Explain the function of a sequencer compare LIFO register.
instruction.
instruction.
CHAPTER 12 PROBLEMS

1. Construct an equivalent sequencer data table for 2. Answer the following with reference to the
the four steps of the mechanical drum-operated sequencer file #B3:0 shown in Figure 12-41:
sequencer drawn in Figure 12-40. a. Assume that output bit addresses O:2/0 through
O:2/15 are controlling associated output pilot

NO
switch Steps
1
2
Motor 3
4

Peg
Figure 12-40 Drum-operated sequencer for Problem 1.

Sequencer and Shift Register Instructions Chapter 12 277

pet73842_ch12_252-280.indd 277 03/11/15 7:20 PM