On Thu, 13 Apr 2000, 권석근 wrote:
> Hi, all.
> Improving RTsupport for uClinux (EZ328) was done.
> internal timer handling code was changed. Instead of using restarting mode,
> new code is using free run mode. this change removed timer overrun
> (occur when TCMP is smaller than interrupt latency).
> It's timing result is very impressive to me. Toggling example (same code as
> release) shows almost no drift. It might be bellow 50 usec. I could not
> say exact
> timing because of my poor analog oscilloscope.
> I'm preparing diff for you, and you could get it soon.
> Some measurement :
> 1) from h/w interrupt to rt_oneshot_timer_irq = ~50 usec
> 2) time for rtl_schduler (priority resolver) = ~80 usec
> therefore time from actual h/w interrupt signal to corresponding rt_task
> is about 130 usec. and this time is almost constant (tested with
> memory logging free-running TCN value and scope). This latency
> could be reduced with asm code but it sacrifies portability and
> easy maintenance. Do not request too much for this little lovely EZ328
> please. :-)
> Q) why need about 130 usec? A) RTIME calc needs more instructions.
> Ping flood test (network load) did not change this value significantly.
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