(Cancelled) Ask help with MC_ReadParam

Ask help to understand documentation for MC_ReadParam

Hi-ya all,

PLC:             S7-1200, CPU1214, Firmware 4.0
Software:     Step7 in TIA Portal V13 SP0 Update 6

I am having a problem with understanding something in the S7-1200 system manual. I would appreciate someone giving some guidance. Please see the highlighted sections in the attached PDF.

(Background)
The root problem is - I am hoping to use the MC_ReadParam instruction to read the position of the motion control. The catch is that the position needs to be captured within a hardware interrupt. A repeatable result is hoped for.. more than a dead-on accurate result. If it was a high speed counter, I would use the style ID1000:P (example).

(Problem)
---------------------------- A
Highlighted in the PDF is the concept "Cycle Control Point (CCP)". I am not sure what that is. I would assume that the term is talking of when normal inputs and outputs are updated. There is no mention of this term again in the S7-1200 system manual. Could someone confirm what CCP is?

---------------------------- B
Next.. There are terms that seem to contradict each other
(blue underline words in PDF page).

First the manual reads:
You use the MC_ReadParam instruction to read single status values, independent of the cycle control point.
Thereafter:
The "MotionStatus" "Position" value updates at each Cycle Control Point (CCP) based upon the current HSC value.

That leads to confusion. If we use MC_ReadParam to extract the <Axis name>.Position value - do we get a recent value or a value at that moment?

Thank you for your attention.
w

My guessing, not theory, not knowledge:

CCP has to be an internal interrupt cycle tme. As many trajectory planners actualy compute position, velocity setpoints recursively, they need to integrate acc, dec, jerk, vel,...to get n+1 velocity, position, therefore the easiest way is to do this in determenistic scheduled times, aka sample time. Simotion has IPO cycle, perhaps S7-1200 has CCP cycle.

Probably the result from each CCP cycle is then transfered trough buffer to the time processing unit (TPU) that sends pulses - which are your needed information on HW interrupt.

Have you seen MC-Servo [OB91] , MC-Interpolator [OB92]? It seems very close to that CCP.

Marko Bursic

Have you seen MC-Servo [OB91] , MC-Interpolator [OB92]? It seems very close to that CCP.

Marko,

Good to hear from you.. thank you.

I'm not familiar with OB91 and OB92 for the S7-1200..
aren't these for the S7-1500?

Your description makes much sense!

Thinking out loud..
For the S7-1200, I believe that this update rate maybe something like 10ms (see LINK) for the S7-1200. If THAT is true - I won't be much of a happy client. {I do miss the old S7-200}

Good chatting to you.
w

It seems something new in v13 SP1.

I have upgraded to v13 SP1, and with CPU with FW 4.1, there exsits OB MC_Interpolator and MC_Servo, but they are protected, you can't write any your code (yet?).

There is also a new type of counting for HSC, that's motion control. No manual regarding this explains what is realy about, but it is possible that is internaly hooked to the PTO of an axis, that would be what you are looking for.

Marko Bursic

I have upgraded to v13 SP1, and with CPU with FW 4.1, there exsits OB MC_Interpolator and MC_Servo, but they are protected, you can't write any your code (yet?).

There is also a new type of counting for HSC, that's motion control. No manual regarding this explains what is realy about, but it is possible that is internaly hooked to the PTO of an axis, that would be what you are looking for.

This Forum already had some questions about the new features.. as you said the feature does not seem to be documented well yet.

Even the new features does not solve mu root problem and by question remains unanswered.

Marko - Thank you very much for your thoughts on the matter. I appreciate it.

w