Page 114 - Programmable Logic Controllers, Fifth Edition

CHAPTER 5 REVIEW QUESTIONS

1. What does the memory map for a typical PLC pro- c. Under what condition is the status bit associated
cessor consist of? with this instruction 0?
2. Compare the function of the PLC program and data d. Under what condition is the status bit associated
files. with this instruction 1?
3. In what manner are data files organized? e. Under what condition is this instruction logically
true?
4. List eight different types of data files used by an f. What state does this instruction assume when it
SLC 500 controller. is false?
5. a. What information is stored in the input image 14. Answer the following with regard to the Output
table file? Energize instruction:
b. In what form is this information stored? a. What part of an electromagnetic relay does this
6. a. What information is stored in the output image instruction look and act like?
table file? b. What is this instruction asking the processor to do?
b. In what form is this information stored? c. Under what condition is the status bit associated
7. Outline the sequence of events involved in a PLC with this instruction 0?
scan cycle. d. Under what condition is the status bit associated
8. List four factors that enter into the length of the with this instruction 1?
scan time. 15. A normally closed pushbutton is connected to a
9. Compare the way horizontal and vertical scan pat- PLC discrete input. Does this mean it must be
terns examine input and output instructions. represented by a normally closed contact in the
10. List the five standard PLC languages as defined ladder logic program? Explain why or why not.
by the International Standard for Programmable 16. Answer the following with regard to a ladder logic rung:
Controllers, and give a brief description of each. a. Describe the basic makeup of a ladder logic rung.
11. Draw the symbol and state the equivalent instruc- b. How are the contacts and coil of a rung
identified?
tion for each of the following: NO contact, NC c. When is the ladder rung considered as having
contact, and coil. logic continuity?
12. Answer the following with regard to the Examine If 17. What does the address assigned to an instruction
Closed instruction: indicate?
a. What is another common name for this
instruction? 18. When are input branch instructions used as part of
b. What is this instruction asking the processor to a ladder logic program?
examine? 19. Identify two matrix limitations that may apply to
c. Under what condition is the status bit associated certain PLCs.
with this instruction 0? 20. In what way does an internal output differ from a
d. Under what condition is the status bit associated discrete output.
with this instruction 1? 21. A normally open limit switch is to be programmed
e. Under what condition is this instruction logically to control a solenoid. What determines whether an
true? Examine-on or Examine-off contact instruction is used?
f. What state does this instruction assume when it
is false? 22. Explain the purpose of Windows based program-
13. Answer the following with regard to the Examine If ming software such as RSLogix.
Open instruction: 23. Briefly describe each of the following PLC modes
a. What is another common name for this of operation:
instruction? a. Program
b. What is this instruction asking the processor to b. Test
examine? c. Run

Basics of PLC Programming Chapter 5 95

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