I have get what is going wrong.

In floasc.inc from Microchip, it allocate something at 0x70, which is
exactly where I was allocating status_temp & w_temp. Then my ISR make use
the function define in floasc.inc. As a result, w & status were never
restored correctly.

Thank you very much to those who have response. I had less understanding
about stack overflow and believe that it was the cause. With your
explanation, I
was able to rule out the possibility, and start looking at other.

WH Tan

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