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Timer1 clarification...

 
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Ted Larson
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Timer1 clarification...
PostPosted: Fri May 16, 2003 11:50 am     Reply with quote

The CCS documentation for the call setup_timer1() states:

"...Timer 1 is a 16 bit timer. With an internal clock at 20mhz, the timer will increment every 1.6us. It will overflow every 104.8576ms."

How can this be true? Why is it that it doesn't increment every 200ns at the instruction cycle rate? Or is the documentation just wrong.

I haven't ever used timer1 before...so, I am just trying to get clear on the units it will return.

Thanks,

- Ted
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Original Post ID: 144514512
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Re: Timer1 clarification...
PostPosted: Fri May 16, 2003 1:22 pm     Reply with quote

:=The CCS documentation for the call setup_timer1() states:
:=
:="...Timer 1 is a 16 bit timer. With an internal clock at 20mhz, the timer will increment every 1.6us. It will overflow every 104.8576ms."
:=
:=How can this be true? Why is it that it doesn't increment every 200ns at the instruction cycle rate? Or is the documentation just wrong.
------------------------------------------------------

It would be true if you used the "divide by 8" prescaler.

The manual has a lot of incorrect examples. You'll notice
on that same page, they have this line:
setup_timer_1 ( T1_INTERVAL | T1_DIV_BY_8 );
Except, there is no "T1_INTERVAL" constant defined in any
of the .h files. It should be T1_INTERNAL.

And for some reason, CCS left out the index (Adobe calls it
"bookmarks") in the latest manual, making it almost useless.
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This message was ported from CCS's old forum
Original Post ID: 144514513
Forest
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Re: Timer1 clarification...
PostPosted: Fri May 16, 2003 6:36 pm     Reply with quote

The manual isn't quite clear in quite a few areas like that.

Have look at the FAQ's - "How is the TIMER0 interrupt used to perform an event at some rate?"
This is for TIMER0 but it goes for the other timers also - the explanation at the bottom helped me.



:=The CCS documentation for the call setup_timer1() states:
:=
:="...Timer 1 is a 16 bit timer. With an internal clock at 20mhz, the timer will increment every 1.6us. It will overflow every 104.8576ms."
:=
:=How can this be true? Why is it that it doesn't increment every 200ns at the instruction cycle rate? Or is the documentation just wrong.
:=
:=I haven't ever used timer1 before...so, I am just trying to get clear on the units it will return.
:=
:=Thanks,
:=
:=- Ted
:=
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This message was ported from CCS's old forum
Original Post ID: 144514518
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