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what is unaligned address access?

I came across  a feature "unaligned address access" in APB4 and started implementing the same. I researched a bit but didnt exactly got what is unaligned address access. Is it same as unaligned transfers that we perform in AXI4?

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  • The alignment of the access refers to the address being a multiple of the transfer size.  For example, an aligned 32 bit access will have the bottom 4 bits of the address as 0x0, 0x4, 0x8 and 0xC assuming the memory is byte addressed.

    An unaligned address is then an address that isn't a multiple of the transfer size.  The meaning in AXI4 would be the same.

    An an aside, I don't believe the APB4 specification discusses address alignment, and you'll find that many APB slaves only accept aligned addresses, since the APB port is normally for basic register accesses

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  • The alignment of the access refers to the address being a multiple of the transfer size.  For example, an aligned 32 bit access will have the bottom 4 bits of the address as 0x0, 0x4, 0x8 and 0xC assuming the memory is byte addressed.

    An unaligned address is then an address that isn't a multiple of the transfer size.  The meaning in AXI4 would be the same.

    An an aside, I don't believe the APB4 specification discusses address alignment, and you'll find that many APB slaves only accept aligned addresses, since the APB port is normally for basic register accesses

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