4 Programmable Logic Controllers Flashcards Preview

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Flashcards in 4 Programmable Logic Controllers Deck (10)
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1
Q

Explain the term cyclic execution.

A
There are four repeating steps:
– Internal Checks
– Reading Hardware Inputs
– Proram Execution
– Writing Hardware Outputs
2
Q

What are the two worst-case assumptions that are made when calculating the
maximum reaction time?

A

The two assumptions are that the input changes just after the inputs are read and
the maximum cycle time is reached.

3
Q

How are maximum cycle time and maximum reaction time linked?

A

Maximum reaction time ≈2· Maximum Cycle time

4
Q

What to do, if reaction time is too long?

A

▪ Optimize Program
▪ Choose more performant PLC
▪ Use interrupts

5
Q

How does the estimation of real-time behavior work?

A

▪ Determine longest program execution path.
▪ Measure or estimate cycle time for this execution path.
▪ Apply formula for maximal reaction time

6
Q

Idea behind the Function Block language (FB):

A

Idea:
▪ Resembling switching circuit design by gates
▪ blocks with input and output

7
Q

Idea behind the Ladder Diagram (LD)

A

Idea:
▪ Resembling switching circuit design by relays („schematics“)
▪ „contacts“ and „coils“

8
Q

What does the “set” command do?

A

set variable to 1

9
Q

What does the “reset” command do?

A

set variable to 0

10
Q

Name three different timer block functions:

A

▪ TON Timer On Delay
▪ TOF Timer Off Delay
▪ TP Timer Pulse