Chapter 8, Problem 11RQ

Program Plan Intro

a.

Programmable Logic Controller (PLC):

• Programmable Logic Controller (PLC) is a specialized computer used in industrial segments to control machines and process.
• PLC is program that consists of a set of instructions which resembles the controlling functions needed to perform specific tasks.
• The function of PLC is similar to that of a relay and hence, in an industrial segment a relay is greatly replaced by a suitable PLC.
• When compared to general Personal Computer (PC), a PLC is available in small and tiny sizes.
• The basic architecture of a PLC consists of an input-output interface module and a small Central Processing Unit (CPU) that runs by control programming language.

PLC counter:

• A counter is a PLC instruction which counts up or down when the input transfers from an off state (false) to an on state (true).
• The three different types of counters instructions are as follows:
  • Up counter
  • Down counter
  • Combined counter

Explanation of Solution

b.

Underflow bit of a down-counter:

• An underflow occurs when the count value goes below its preset value...