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The AXI and AHB protocols handle transaction addresses differently, so the AXI5 to AHB5 bridge must perform address alignment. The AHB protocol does not support unaligned transfers.
In AXI, the master issues only the starting address for the whole transaction and it is the responsibility of the slave to increment the address for the transaction beats. The AXI address can be unaligned to the boundary that axsize[2:0] determines, although it is only the first beat that is unaligned, the remaining beats are aligned. In AHB, the master calculates and issues all beat addresses in a burst and each beat is aligned.
Therefore, the AXI5 to AHB5 calculates aligned AHB addresses for all beats from the incoming single AXI address. The bridge can either align the address or split the AXI transaction into several aligned AHB beats. The bridge also calculates wrap addresses.
When the bridge receives:
A Non-modifiable read transaction is not permitted to perform a speculative read of Device memory, so: