[S5-155U CPU948]about cycle time ?

Hi, everyone.
I read the CPU948 programming guide, it say cycle time is including that:

The cycle time therefore includes the following:
· the time required to process the cyclic program (system and user
program),
· the time required to process interrupts (e.g. time-controlled
interrupt),
· the time required to process interruptions (errors).

It mean 1 cycle time = run program time + interrupt time + process errors time?? right??
If my program have a timer, it'll work 10s. The CPU will wait 10s to end this cycle time, and restart next cycle time ?? right?? When CPU wait , nothing can do ?? Is it right??

Or CPU use other method to work?? Hope you can explain relative between cycle time and CPU. Thank you!! Thank you !!

The cycle time is the time the PLC takes to complete processing the program. It goes something like:

1 READ Inputs
2 Process Program as called from OB1
3 WRITE Outputs.

This on average, depending on program could be anything from 20mS to 100mS.

If you have timed or hardware interupts blocks, these will take some process time, not much though <1mS depending on code.


If you have a 10 second timer, the program will examine its condition every scan until the 10 seconds are up, as it reaches that part of the program. So no, the CPU does not hang up for 10 seconds, it continues looking at the timer condition as well as every other instruction, one instruction at a time through the entire program.

If your scan is 100mS, then it would have completed 100 scans by the time the timer completes.

Apple,

I think...

It mean 1 cycle time = run program time + interrupt time + process errors time?? right?? YES
If my program have a timer, it'll work 10s. The CPU will wait 10s to end this cycle time, and restart next cycle time ?? right??NO When CPU wait , nothing can do ?? Is it right??NO

Click to expand...

Your CPU scan is...

Look at inputs
Look at OB
Look at jump to subroutine/s FB….during this time your timer is timing
Any program interrupt
Errors (we have none)
Set outputs
Look at inputs.....

Look here [url="http://www.plcs.net/chapters/howworks4.htm"]http://www.plcs.net/chapters/howworks4.htm[/url]
And here [url="http://www.plcs.net/chapters/timeacc17.htm"]http://www.plcs.net/chapters/timeacc17.htm[/url]

Timers and counters slow down the scan time but they do not stop it.
Hope it helps


Edit: Peter is faster...but at least I was correct