Spurious IRQ7

[Angelo Fraietta]

Grigori Khmyrov wrote:
> I have problem with extra interrupts at i686 industrial computer.
> It never happened before with old VIA C3 400 MHz (100x4.0) board.
> But I have an extra interrupts with new one VIA C3 667 MHz (133x5.0).
> We have a hardware which produces signal every 5 ms. We use the signal 
> as IRQ7.
> Very rear I see an extra call of interrupt handler. Spurious IRQ7 
> happens. I'm sure
> that our hardware is not producing that signal. Is it any suggestion 
> what can be
> wrong. Can it be 8259A Interrupt Controller or RTEMS?
> I'm using RTEMS 4.6.2 with i486 BSP.
> Any suggestion how to fix or catch a problem appreciated.
> 
What does the signal look like with a CRO?
You might be getting reflections back that are causing reflective spikes 
(this happened to me and appeared as extra pulses) so check your impedances
-- 
Dr Angelo Fraietta

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