S7-1200 CTRL_HSC_EXT Frequency Help / Sample

I've been beating my head against the wall for half a day now trying to get the CTRL_HSC_EXT instruction to work to simply measure the input Frequency of input I0.0 on a S7-1200 CPU 1214C PLC  (Firmware V4.2) but no matter what I do it always reads 0 Hz.

Has anyone else had any luck with this and have an example or advice on what I could be missing?  I've read and re-read the system manual's description on how this should  work and believe I have done exactly what it talks about with no luck.

 Did you try to change the Input Filter settings in the Digital Input configuration to a lower Time period say 0.8 millisec or similar and try to compile the hardware config again and download the config?

Xorrox

I've been beating my head against the wall for half a day now trying to get the CTRL_HSC_EXT instruction to work to simply measure the input Frequency of input I0.0 on a S7-1200 CPU 1214C PLC  (Firmware V4.2) but no matter what I do it always reads 0 Hz.

Has anyone else had any luck with this and have an example or advice on what I could be missing?  I've read and re-read the system manual's description on how this should  work and believe I have done exactly what it talks about with no luck.

 

Well it's fixed!  However I'm still not sure what fixed it: but I suspect it had something to do with downloading the hardware configuration so thank you very much!!  Here is what I did:

• I checked and confirmed that I had changed the I0.0 filtering (to its fastest setting of 0.1 usec).  I had done multiple downloads with this setting and it was still not working.
• Since I was looking at the hardware configuration I thought I would try enabling the rising and falling edge detection on my I0.0 input to see if that had any effect.  When I downloaded that it started to work!  However, I had also cycled power to the PLC around the same time so I'm not sure which did the trick.
  
• Since I couldn't find anything in the documentation that said the edge detection is required, I again disabled the edge detection, downloaded and it was still working.
• I then tried slowing down the filtering and it did stop working even without cycling power to the PLC.
• Finally I set it back to my original I0.0 filtering (to its fastest setting of 0.1 usec) with no edge detection and its still working.
  

• Download new hardware filtering value.  Cycle Power (I don't think this is required but who knows).  If it still does not work, I will try: enable edge detection> download> see if its working> if yes > disable edge detection and see if it is still working.