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Interrupt arbitration on MPC555


Hi,

I have some problems with interrupt arbitration on the MPC555. This
microcontroller has a number of on-chip peripherals like CAN controllers,
Serial controllers etc. These peripherals can be assigned (by software) an
interrupt priority from 0(highest) to 31(lowest).

The MPC555 is build around a powerpc-core and handles 8 interrupt levels. It
is clear that some kind of arbitration is needed (comparable to what is
available for the powerpc version of eCos).

The interrupt priority of the peripheral determines the interrupt level (and
hence the arbitration), priorities o to 6 are mapped to levels 0 to 6,
priorities 7 to 31 are all mapped to level 7.

I suppose not every application is interested in using the same priorities,
some might like to assign a high priority to CAN-interruipts and do not even
use the TPU, for another application it might be necessary to assign a
higher priority (and hence different arbitration) to the TPU than the
CAN-controller. These are strong arguments to assign these priorities and
setup the arbitration somewhere during startup of the APPLICATION.

On the other hand, it also makes sense to use device drivers for can, serial
ports etc,... These device drivers have to create interrupts and hence have
to know the priority of these interrupts. So it seems you have to set-up
priorities and arbitration somewhere within ECOS. And then you lose all
flexibility ....

Any suggestions ???

Regards,
Bob

------------------------------------------------------------------------
ir. Bob Koninckx
Katholieke Universiteit Leuven
Division Production Engineering,                      tel. +32 16 322535
Machine Design and Automation                         fax. +32 16 322987
Celestijnenlaan 300B                 bob.koninckx@mech.kuleuven.ac.be
B-3001 Leuven Belgium            http://www.mech.kuleuven.ac.be/pma.html
------------------------------------------------------------------------



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