restart counter CNT

Fab

Hello,

Is it possible to restart to zero the counter cnt of the propeller, or I should use the ctra or crtb ?
I measure a duration in a repeat loop and i have some problems. I think that sometimes i'm at the end of the counter

thank you

Post Edited (Fab) : 7/13/2010 7:54:14 AM GMT

MagIO2

You can't set CNT to zero - at least not without restarting your program ;o). And if you do your measurement correctly, you don't have to.

startCnt:= CNT
' do your stuff
endCnt := CNT

ticks := endCnt - startCnt
time := ticks / clkfreq

You start having problems, when the part in 'do your stuff' takes longer than ~52 seconds because then the counter will overflow and start from the beginning again.

Ale

What is that guy/gal Vikram talking about ?... I thought it was some sort of sarcasm... but looking at his posts counter... makes me think: spam !

The counters and CNT are nicely explained not only in the manual but also in the application note about the counters (AN001 ?). But what MagIO2 wrote may just what you need. Do not forget the overhead that reading the CNT register has (you get that value just reading two times the CNT in a row).

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OMU for the pPropQL/020 propeller.wikispaces.com/OMU
pPropellerSim - A propeller simulator for ASM development sourceforge.net/projects/ppropellersim

Fab

It's ok, but i'm using CNT in a repeat loop and I think that in some cases between "start" and "end" the counter restarts.

repeat 
     waitpne( |<pin, |<pin, 0)      
     waitpeq( |<pin, |<pin, 0)      
     start:=cnt                       
     waitpne( |<pin, |<pin, 0)      
     waitpeq( |<pin, |<pin, 0)
     end:=cnt                            
     T := (end-start)  
     
     if T<....
     .....

I have 2 sensors and I want to compare the duration between two rising edges ( on "pin" ) on each sensor[noparse][[/noparse]code]

Post Edited (Fab) : 7/13/2010 5:10:04 PM GMT

mpark

The counter may well restart but that won't affect the difference between start and end.

Fab

Ok thank you
I actually found my error, during the calculation I had to use floats variables and I did not define the object FloatMath.
effectively the counter restart but don't affect the difference between start and end.