Anders Garder

MCF54454 with branch cache hangs my flexbus?

Discussion created by Anders Garder on Mar 30, 2011
Latest reply on Mar 31, 2011 by Anders Garder


I am having trouble with sporadic reads to unmapped flexbus memory causing

the processor to hang until the bus monitor kicks it going again.


The accesses seem to come from the branch cache, something like


move.l #1000,a2


lea sdram_label,a2

jsr (a2)


will still have caused a flexbus access at address 1000.


Turning the branch cache off comes with a 10% performance decrease which is no good.


I can extend an auto acknowledging chipselect to cover flexbus memory, what if a2 would point to

internal peripheral space?


Does anyone know if I am right about this? If so, can instruction prefetch disturb the internal peripherals?



best regards