RapidIO: The Next Generation Communication Fabric For Embedded Application

4.5. WRITE OPERATIONS

The Type 5 packet format supports write (Figure 4.7), write with response (Figure 4.8) and atomic (read-modify-write) operations. Type 5 transaction packets always contain a data payload. A data payload that consists of a single double-word or less has sizing information. The WRSIZE field specifies the maximum size of the data payload for multiple double-word transactions. The fields, WRSIZE and WDPTR, are used to specify the size of the data pay-load and are encoded the same way that the RDSIZE and WDPTR fields specify the size of the data for a read operation. Aside from the data payload, the fields of the Type 5 Write transaction packet (Figure 4.9) are essentially the same as for a Type 2 Request transaction.

Figure 4.7. Write operation

Figure 4.8. Write with response operation

Figure 4.9. Type 5 packet format

Table 4.4. Write class transaction types

Encoding	Transaction field
0b0000–0011	Reserved
0b0100	NWRITE transaction
0b0101	NWRITE_R transaction
0b0110–1101	Reserved
0b1110	ATOMIC test-and-swap: read and return the data, compare with 0, write with supplied data if compare is true
0b1111	Reserved

Write transactions may request the sending of a response or not. ...