The NoC request packet from the NMU carries the following:
- Triple {Source ID, AXI-ID, Tag} for read requests
- {Source ID, AXI-ID} for write requests
Non-DDR memory controller NSUs send a compressed AXI-ID to the downstream AXI slave. The programmable compression modes are as follows:
- A 2-bit compressed AXI-ID is created by selecting any two bits of the {Source ID, AXI-ID}. The NSU configuration programs the bit selection.
- A 2-bit fixed value determined by a configuration register. This mode effectively forces read and write requests to remain in order.
By default the NSU selects the least significant two bits of the request AXI-ID as the compressed ID. DDR memory controller NSUs do not compress the AXI-ID.