Chapter 8, Problem 1P

Program Plan Intro

COUNT-UP (CTU) Counter:

• The CTU counter refers to an up counter.
• This counter is used to count an event that occurs logically or externally and places that value in the counter’s accumulator.
• The accumulated value can even be maintained during false rung conditions and can be reset back to 0 using reset instruction.

Explanation of Solution

b.

Energizing output “O:2/0”:

• The accumulated value of CTU will be incremented by one whenever it receives the conversion input “false-to-true”.
• The DN signal bits will get activated once the accumulate value attains the preset value...

Explanation of Solution

c.

Energizing output “O:2/1”:

• In the given program, “rung 3” does not allow the DN signal bits.
• It means that the output “O:2/1” will be activated for the values which are less than the preset value...

Explanation of Solution

d.

Computing accumulated value:

• Usually the accumulated values of the Programmable Logic Controller (PLC) counters will retain its values even during power off.
• It restores the values until it get the power back...

Explanation of Solution

e.

Accumulated value of the counter:

• The reset mode has been available in the “rung 4” which contains same address “C5:1” of CTU counter.
• The accumulated value of CTU counter will be reset to zero when the “rung 4” turns into “true”...

Explanation of Solution

f.

Situation when the count gets incremented:

• When the “rung 1” input ‘I:1/1” throws “off-to-on” conversion signals, the CTU counter will start its counting process...

Explanation of Solution

g.

Situation when the count gets reset:

• The reset mode will be activated when the “rung 4” becomes true...