RapidIO: The Next Generation Communication Fabric For Embedded Application

4.8. MAINTENANCE OPERATIONS

The Type 8 MAINTENANCE packet format (Table 4.5) is used to access the RapidIO capability and status registers (CARs and CSRs) and data structures. Unlike other request formats, the Type 8 packet format serves as both the request and the response format for maintenance operations. Type 8 packets contain no addresses, and contain only data payloads for write requests and read responses. All configuration register read accesses are performed in word (4-byte), and optionally double-word (8-byte) or specifiable multiple double-word quantities up to a limit of 64 bytes. All register write accesses are also performed in word (4-byte), and optionally double-word (8-byte) or multiple double-word quantities up to a limit of 64 bytes.

The WRSIZE field specifies the maximum size of the data payload for multiple double-word transactions. The data payload may not exceed that size, but may be smaller if desired. Both the maintenance read and the maintenance write request generate the appropriate maintenance response.

The maintenance port-write operation is a write operation that does not have guaranteed delivery and does not have an associated response. This maintenance operation is useful for sending messages such as error indicators or status information from a device that does not contain an end point, such as a switch. The data payload is typically placed in a queue in the targeted end point and an interrupt is typically generated to a local processor. A port-write ...