Mayank Kaushik
Guest
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 Posted:
Tue Jan 11, 2005 12:11 am Post subject:
Doubt about interrupt handling in AT91 |
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Hi,
Im an undergrad student, with an experience of the past 15 days on the
AT91RM9200, the first uC ive worked with, besides the one week spent on
an 89c51, so im a real greenhorn to embedded systems. I am confused
about why we need to change the mode or the ARM core from irq to
sys..the atmel notes mention that the link register and the spsr would
be overwritten if another interrupt occurs..in that case, why can we
not just push the values of the above registers the stack, and stay in
the same mode?
also, when an interrupt occurs, the value stored in the register r14 is
PC +4..whys the 4 added??
thanx in anticipation
Mayank |
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