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ARM7TDMI processor mode

shan S over 12 years ago

Note: This was originally posted on 23rd November 2012 at http://forums.arm.com

I am using the ATMEL91SAM7SE512 controller with ARM7TDMI processor.The application is running in the User mode .

when the interrupt(IRQ) occurs processor must switch to IRQ mode,then it should go to the IRQ handler routine.

here application developer part is to tell the IRQ handler address only.so who taking the responsibility to change from User mode to IRQ mode.

whether the core itself switched into IRQ mode using hardware setup or some low level routines(program) avail.i struck in this point , i cant

proceed further on this study of ARM7TDMI processor.

please tell me your thoughts regarding this query.

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thanks
shan.s

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Martin Weidmann over 12 years ago

Note: This was originally posted on 26th November 2012 at http://forums.arm.com

I think what you missing is that these steps (CPSR -> SPSR_irq, updating the CPSR and branching to the vectors) are ALL AUTOMATIC. That is the hardware does it for you when it recognizes the IRQ exception.

So you are correct - the User mode software would not be able to perform these steps. But that does not matter, as it is the hardware that is taking care of it.
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Martin Weidmann over 12 years ago

Note: This was originally posted on 26th November 2012 at http://forums.arm.com

I think what you missing is that these steps (CPSR -> SPSR_irq, updating the CPSR and branching to the vectors) are ALL AUTOMATIC. That is the hardware does it for you when it recognizes the IRQ exception.

So you are correct - the User mode software would not be able to perform these steps. But that does not matter, as it is the hardware that is taking care of it.
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