Question regarding time value, simatic

[Daye.04]

Hey all. I've got a query for you.

Does it require more of the processor of a PLC to generate the time value everytime a timer is called upon, rather than using a time value stored in a datablock register?

 

[L D[AR2P#0.0]]

Post examples of both methods

 

[Daye.04]

Rightio

And then via Datablock

 

[JesperMP]

Your second image doesnt display, but maybe you are using the IEC TON block which requires its own IDB.

The S5timers has much shorter execution time than the IEC TON. But the S5Timers are arcaic and limited in numbers and functionality. I recommend that you dont worry so much about the execution time and use the IEC TON instead.
Todays CPUs are so fast that it is no longer so important to worry about execution times as it used to be.

 

[Daye.04]

It doesn't? Blimey!

But actually. Both timers are of the exact same type.

And the reason I'm asking about this is not becuase of my own worries - it's rather to make sense of this program I'm trying to figure out. And so I'm trying to understand why the person who made the program has used two different methods interchangably

 

[JesperMP]

Now it displays on my PC.

OK, the difference is that one has a constant S5time and the other has a variable S5time for the setpoint. That is the difference.

 

[L D[AR2P#0.0]]

The method using the DB will take more memory and take longer to execute than the method where the time value is specified as a constant.

The DB method was most likely used during development so the timer value could be changed via a HMI or VAT table without having to make continual code changes.

 

[JesperMP]

The DB method may be used also after development. The enduser may need to be able to change the timer setpoint on his HMI.

 

[Daye.04]

Hmm. Yeah, that makes sense. Thanks ^^