James,
     Let me change my wording a little bit here. Won't those two=20
instructions put the settings back to the proper values so that the=20
timer counts the proper number of cycles to give me the 100mS delay?
Thanks,
rich!

On 7/21/2014 11:34 PM, James Cameron wrote:
> On Mon, Jul 21, 2014 at 11:09:04PM -0500, Richard R. Pope wrote:
>> Joe,
>>       My resettimer function does this:
>>           resettimer()
>>           {
>>               TMR1H =3D 0x0B;
>>               TMR1L =3D 0xDC;
>>           }
>>       Doesn't that set the timer registers back to 0 and as soon as I
>> turn the timer back on it will count to the proper value for 100mS?
> No, that sets the timer to 0xbdc, or 3036 decimal.  THR1H and TMR1L
> together make up a 16-bit counter, H means high byte, L means low
> byte.
>
> When the timer is allowed to run, it will count up and overflow to zero,
> and when it reaches zero an interrupt will trigger and your ISR will
> be started.
>
> This technique is called preloading the timer, as opposed to free
> running the timer.
>
> The number of counts will be 0x10000 minus 0xbdc, which is 62500.
>
> How this relates to instruction cycles will depend on a prescaler
> configuration.
>
> (By the way, if you read the timer in your ISR you will find it
> advanced from zero by as many instruction cycles as were required to
> get to that point in the ISR.)
>

--=20
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