question on Exclusive access

Martin has hopefully answered your first question, although a simpler way of answering might simply be to state that exclusives are there to support read-modify-write sequences, so a read is always the first step in the sequence.

For your second question, the exclusive access monitor is not part of the interconnect. It is usually part of the destination target device, so any write response the monitor returns will need to factor in both whether the exclusive nature of the transfer completed successfully or not, and also the OKAY/ERROR nature of the transfer.

So if the exclusive write was a "non-bufferable" write, the response returned on BRESP will indicate if the transfer completed exclusively, and also if the transfer was stored in the "S0" destination.

I said above that the monitor is "usually" part of the destination device. This can be fully integrated with it, or perhaps a standalone monitor attached to the destination device. But it could also be further away from the final destination device, as long as it is able to see all transfers that can access the final destination device.

Martin has hopefully answered your first question, although a simpler way of answering might simply be to state that exclusives are there to support read-modify-write sequences, so a read is always the first step in the sequence.

For your second question, the exclusive access monitor is not part of the interconnect. It is usually part of the destination target device, so any write response the monitor returns will need to factor in both whether the exclusive nature of the transfer completed successfully or not, and also the OKAY/ERROR nature of the transfer.

So if the exclusive write was a "non-bufferable" write, the response returned on BRESP will indicate if the transfer completed exclusively, and also if the transfer was stored in the "S0" destination.

I said above that the monitor is "usually" part of the destination device. This can be fully integrated with it, or perhaps a standalone monitor attached to the destination device. But it could also be further away from the final destination device, as long as it is able to see all transfers that can access the final destination device.