Programmable auto-reload Timer output?

[Chen]

I am using PIC18F8620, and I need a varible clock to pace my operation.

Is there a programmable auto-reload timer output? (up to MHz range)
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Original Post ID: 11365

[Neutone]

:=I am using PIC18F8620, and I need a varible clock to pace my operation.
:=
:=Is there a programmable auto-reload timer output? (up to MHz range)

If I get your question right.
Concider doing this from main;
Use the internal 16 bit timer

while(true)
{ if(timer overflow interupt flag is set)
{ Set_timer(variable time)
Clear timer interupt flag
Perform what oprtations you must
}
}

This does not require using an interupt. It only checks the interupt flag. You basicly gate your operatios to a time interval that is variable with the value you load into the timer.
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Original Post ID: 11366

[Chen]

Thanks for your suggestion, but

I prefer no PIC is involved at all after the clock started

Also, your approach seems to change the clock a little depending on when the Set_timer(variable time)is called.



:=If I get your question right.
:=Concider doing this from main;
:=Use the internal 16 bit timer
:=
:=while(true)
:={ if(timer overflow interupt flag is set)
:= { Set_timer(variable time)
:= Clear timer interupt flag
:= Perform what oprtations you must
:= }
:=}
:=
:=This does not require using an interupt. It only checks the interupt flag. You basicly gate your operatios to a time interval that is variable with the value you load into the timer.
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This message was ported from CCS's old forum
Original Post ID: 11368

[Sherpa Doug]

:=:=I am using PIC18F8620, and I need a varible clock to pace my operation.
:=:=
:=:=Is there a programmable auto-reload timer output? (up to MHz range)
:=
:=If I get your question right.
:=Concider doing this from main;
:=Use the internal 16 bit timer
:=
:=while(true)
:={ if(timer overflow interupt flag is set)
:= { Set_timer(variable time)
:= Clear timer interupt flag
:= Perform what oprtations you must
:= }
:=}
:=
:=This does not require using an interupt. It only checks the interupt flag. You basicly gate your operatios to a time interval that is variable with the value you load into the timer.

How about subtracting a fixed value from the timer instead of setting it. Then it can count a few ticks before you poll the flag with no accumulated error.

The only stand-alone chips that I know of that do this are dedicated synthisizer chips which generally work at many MHz and draw lots of power. Look at an AD9853 for example. I briefly looked at it for a project untill I saw it takes 500mA supply current!!!

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This message was ported from CCS's old forum
Original Post ID: 11370

[Richard Slater]

:=I am using PIC18F8620, and I need a varible clock to pace my operation.
:=
:=Is there a programmable auto-reload timer output? (up to MHz range)

Maybe a programmable frequency synthesiser from Cypress is what your looking for? Look under 'Programmable Clocks' on their website. I am currently including their CY22150 in a project, available for a few dollars from Digikey.


Good luck

Richard

Richard
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This message was ported from CCS's old forum
Original Post ID: 11467