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PCI IO illegal addressing
Dear PCI Wizards,
I have a question regarding IO addressing.
AD[1:0] identify the least-significant byte within the target doubleword.
It is illegal for the initiator to assert any byte enables of lesser significance than the one indicated by AD[1:0].
For example, it is illegal for AD[31:0] to be 0x00001002 and for CBE#[3:0] to be 0x0. In this case the target must assert target abort.
My question is what happens if AD[31:0] is 0x00001000 and CBE#[3:0] is 0x4? Is this legal or do I have to access from byte zero and up?
The same question when AD[31:0] is 0x00001002 and CBE#[3:0] is 0x8? Is this legal or do I have to access from byte 2 and up?