Cortex-A8 debug issues

Hi expert

Since I debug AM3354(Cortex-A8 Core), I want to enable IRQ, so I write the assembler code:

IntrEnableIrq

    MRS     R0, CPSR             ; Pickup current CPSR
    BIC     R0, R0, #0X80        ; Clear interrupt lockout bits in CPSR
    MSR     CPSR_c, R0           ; Setup new CPSR value
    MOV     pc, lr               ; back 

and I put a break point in 

MSR CPSR_c,R0

and I run the program in full speed, then stop in MSR CPSR_c, then I run the program again,

but the program come to hard fault immediately.

I am sure the program run to error immediately, even not come to MOV pc, lr.

So I check the CPSR register's bits value, 

Bit7(IRQ set bit is cleared) .

It is really confused me a long time, ARM Mode is 10111(ABT mode), and I can change IRQ(bit 7)from 1 to 0, then the program 

come to error immediately , why this happen? I really need your help.

Best Regards

Jack

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  • Hi ,

    The MSR instruction should not cause an abort, but maybe servicing a pending interrupt immediately after unmasking causes the abort exception?

    You might want to look at the SCTLR and VBAR registers.

    Also, you can determine the vector from the exception PC, which will tell you if this is a data abort or a prefetch abort exception.

    Best regards,

    Vincent.

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  • Hi ,

    The MSR instruction should not cause an abort, but maybe servicing a pending interrupt immediately after unmasking causes the abort exception?

    You might want to look at the SCTLR and VBAR registers.

    Also, you can determine the vector from the exception PC, which will tell you if this is a data abort or a prefetch abort exception.

    Best regards,

    Vincent.

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