Transaction Lifecycle in CHI

How a simple memory request travels through the NoC (Network on Chip).

Step-by-Step: Read Shared

  1. REQ: The Request Node (RN-F) sends a `ReadShared` message to the Home Node (HN-F).
  2. Snoop: The HN-F checks its Snoop Filter. It sees that RN-B has the data. It sends a `Snoop` request to RN-B.
  3. RSP: RN-B responds that it has the data.
  4. DAT: RN-B sends the data to RN-F (or to HN-F depending on the configuration).
  5. ACK: RN-F sends a completion acknowledgment back to the HN-F.
Beginner Note: Unlike AXI where data flows on the same channel as the handshake, in CHI, the data and response can arrive at different times and even take different paths!