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Q: Why ARM generates undefined instruction exception but PC and instruction are both OK

Dear All,

I have met some problem which holds me for almost 2 weeks. I worked on some ARM926EJ-S based chip. The code sometime can run up to 2-3 days with no problem, but sometime after few hours running, ARM generated "undefined instruction" exception. I use the ICE debugger to trace the problem, the value in "lr" is good, in terms of it is within well defined code area. So I did one experiment, in the "undefined exception handler", I just simply set the PC back to the "lr", and the code can resume without any problem. In my case, I turn on the Icache and Dcache.
Does anyone have the similar experience before? or Any idea? Thanks a lot!

Ys1234