RapidIO: The Next Generation Communication Fabric For Embedded Application

7.5. TRANSACTION AND PACKET DELIVERY ORDERING RULES

Because RapidIO transactions must support both multiple transaction priorities as well as causality and deadlock avoidance, delivery ordering rules must be established to ensure that the system operates properly at all times. The rules specified in this section are required for the physical layer to support the transaction ordering rules specified by the higher layer RapidIO specifications.

Transaction Delivery Ordering Rules:

1. The physical layer of an end point processing element port shall encapsulate in packets and forward to the RapidIO fabric, transactions comprising a given transaction request flow in the same order that the transactions were received from the transport layer of the processing element. (Packets with the same source ID, destination ID and priority level must remain in order with respect to each other).

2. The physical layer of an end point processing element port shall ensure that a higher-priority request transaction that it receives from the transport layer of the processing element before a lower-priority request transaction with the same sourceID and the same destinationID is forwarded to the fabric before the lower-priority transaction. (Lower-priority packets can't pass higher-priority packets).

3. The physical layer of an end point processing element port shall deliver transactions to the transport layer of the processing element in the same order that the packetized transactions were received by the port. ...