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ARM assembler register read

Dennis Gabler
Note: This was originally posted on 11th September 2010 at http://forums.arm.com

Hello All,

I need a quick example of how to place a value from a hardware register (0x70001234 for example) into a register such as R0
then compare it to a constant such as 0xE0680003 and do a branch based on equality.

So far I have had no luck getting something this simple to work.

Thanks,
Dennis
Parents
  • Note: This was originally posted on 14th September 2010 at http://forums.arm.com

    Thank you, I was not sure what that construct actually assembled to. Makes more sense now.

    ldr     r1, =(SBMR)

    --> This code will not read a RAM/Peripheral register. The parenthesis is treated by the assembler to contain an equation of sorts that eventually results to a constant. Thus, this code boils down to ldr, r1, = constant.

    See my example and study it. Also read the Assembly instruction sets manual from ARM. The books by Sloss and Hohl are very good place to start with.
Reply
  • Note: This was originally posted on 14th September 2010 at http://forums.arm.com

    Thank you, I was not sure what that construct actually assembled to. Makes more sense now.

    ldr     r1, =(SBMR)

    --> This code will not read a RAM/Peripheral register. The parenthesis is treated by the assembler to contain an equation of sorts that eventually results to a constant. Thus, this code boils down to ldr, r1, = constant.

    See my example and study it. Also read the Assembly instruction sets manual from ARM. The books by Sloss and Hohl are very good place to start with.
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