Chapter 10, Problem 3P

Program Plan Intro

Timer:

• Timer is special type of clock used to measure some specific time intervals.
• Three types of timer
  • Delay-OFF Timer
    • Delay-OFF timer is activated when it is turned on and does not wait for the entry of input.
    • It is used to count downwards from the programmed time.
    • The value of timer is cleared when the enabling input is in off state.
  • Delay-ON Timer
    • Delay-ON timer is activated by its input.
    • It is used to count upwards to the programmed time.
    • The value of timer is cleared when the enabling input is in off state.
  • Delay-ON-Retentive Timer
    • Delay-ON-Retentive Timer is activated by the inputs and starts accumulating time.
    • It retains the accumulated value even if the rung goes false.
    • It can be reset only by RESET command.

Thumbwheel switch:

• Thumbwheel switch is a switch which is used to convert numerical values displayed on disk where the numbers are converted into binary, decimal and hexadecimal values.
• It contains a function called lock which helps to retain the preset value from being modified.
• It can be operated only by a thin object like pen tip.