Emulating clock ISR

Ingolf Steinbach Ingolf.Steinbach at jena-optronik.de
Wed Apr 4 11:18:22 UTC 2007

Hash: SHA1


we have the following problem:

On leon2, the RTEMS clock is based on the Interrupt
for Timer1 which is hard-wired to priority 8. We have
one "own" external interrupt which may not be interrupted
by another ISR.

We can only assign interrupt priorities in the range
4 to 7 (i.e. less than the clock interrupt) to our
own interrupt source.

By analyzing the interrupt mask register, we found
that no interrupts with priority > 8 are enabled, so
the above Clock interrupt is the only problem.

Our proposed solution is to disable timer1 (and the
associated interrupt 8) completely and instead use
another external(!) interrupt source with a priority
less than our important interrupt which is then
asserted with 1MHz.

Is this feasible (from RTEMS's point of view)?
What should be called from the ISR for this new
clock interrupt? Is calling rtems_clock_tick()

Kind regards
- --

Ingolf Steinbach
Software Engineer

Jena-Optronik GmbH
Prüssingstraße 41
07745 Jena
Tel: +49 3641 200-216
Fax: +49 3641 200-220
E-Mail: ingolf.steinbach at jena-optronik.de

President & CEO: Dietmar Ratzsch I CFO: Dr. Harald Bruhn
Sitz der Gesellschaft: Jena  l  Handelsregister: AG Jena HRB 201.869

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