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Cortex R8 axi unaligned transfer

Ben Chen

I have an issue in my retarget printf study

AXI master port have not any transfer when I change address to unaligned address

There is my C code

volatitle int *tube = (volatile int *)0xfc000000;

*tube = ch;

I change the address to 0xfc000001;

I not sure this usage is legal or not in Cortex-r8.

Or my C program has not recommended style.

Thank for your help!

  • +1 Arm Employee Badge

    Unaligned accesses are only allowed to memory that is marked as normal in the MPU (or default memory map.) Unaligned accesses to normal memory must also be enabled by setting SCTLR.A==0.

  • 0 in reply to Peter Rielly

    Thank for your reply. I check our design SCTLR.A is zero.

    I send two accesses  One is normal access and the other is unaligned access.

    Final only first access in my waveform

    I think somthing is wrong in my program or design will auto mask not supported access

    1.  *(volatile int *) 0xfc000000 = 0xffff; 

    2.   *(volatile int *) 0xfc000001 = 0xffffff00;

    Thank you!