[ECOS] Re: Timer mechanism

Savin Zlobec savin@elatec.si
Wed Jan 14 13:09:00 GMT 2004


Giovanni Perbellini wrote:

>Hi all,
>
>I'd like to know how the timer mechanism works.
>I have used a function to return the current time, cyg_current_time().
>I guess that this function returns the ticks count since when I turn on the
>board, is it correct?
>  
>
Yes - since eCos started.

>Otherwise, Is there a variable, method or class returning/containing the
>ticks count since the power up?
>
>Moreover, I have read that there is a macro to read the current value of the
>timing devices counter since the last interrupt, called HAL_CLOCK_READ. What
>is the relationship between the tick and interrupt?
>
The timing device is usually a hardware timer which can generate an 
interrupt after a
specified amount of internal ticks. This timer gets initialized with 
HAL_CLOCK_PERIOD
which "is" 10ms (by default) in hw timer ticks. The HAL_CLOCK_READ macro 
returns
the number of hw timer internal ticks elapsed since the last interrupt.

savin


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