S7 timers

[spaderkung]

Hello,

How are timers handled in the otherwise so linear program scan?

Will a 5 ms on 5 ms off cyclic timer in a function block called once every scan of 60 ms have a 10 ms period?

If a timer output in a FC early in the scan enables a timer in another FC late in the scan - will there be almost 1 scan cycle delay of the start of the second timer?

/Jon

 

[L D[AR2P#0.0]]

What sort of timers, IEC or S5 ?

Which S7 CPU are you using ?

How are you generating the 50ms on 50ms off ?

 

[PeterW]

Hello,

How are timers handled in the otherwise so linear program scan?

Will a 5 ms on 5 ms off cyclic timer in a function block called once every scan of 60 ms have a 10 ms period?

If a timer output in a FC early in the scan enables a timer in another FC late in the scan - will there be almost 1 scan cycle delay of the start of the second timer?

/Jon

No


Yes





EDIT:

As a footnote, these would be the same answers for any PLC.

 

[spaderkung]

At the time of the question it was the S5 timer on S7-3x. I have since learned of the IEC timer and that the S5 timer is implemented on a lower level in the hardware. This would also explain the restrictions due to different processors as the timers require some (or at least more) multitasking as opposed to the linear scan.

The underlying question is how much "PLC"-functionality that can be programmed on a 8-bit MCU. Suitable for linear programming, challenging for multitasking and nested interrupts.