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7. UltraSPARC External Interfaces
7.17.2 Packet Description
7.17.2.1 Master ID (MID)
MID is a 5-bit field. It identifies the source Interconnect master port that made
this request. MasterID is the same as the port_ID bits. SC can be useMID to main-
tain ordering for transactions with the same MID, and to parallelize requests with
different MIDs.
If the system forwards the request to a slave UltraSPARC for proxy execution, the
slave maintains the MID and returns it to SC in the P_REPLY packet.
7.17.2.2 Transaction Type
This 4-bit field encodes the transaction type, as shown in Table 7-37.
7.17.2.3 Class
The Class bit identifies which of the two master Class queues the request has
been issued from. The system must maintain strong ordering between transac-
tions with the same Class bit and MID field.
Table 7-37 Interconnect Transaction Type Encoding
Transaction Type Name Type
P_RDS_REQ ReadToShare 0000
P_RDSA_REQ ReadtoShareAlways 0001
P_RDO_REQ ReadToOwn 0010
P_RDD_REQ ReadToDiscard 0011
S_CPB_MSI_REQ CopybackGotoSstate 0100
P_NCRD_REQ NonCachedRead 0101
P_NCBRD_REQ NonCachedBlockRead 0110
P_NCBWR_REQ NonCachedBlockWrite 0111
P_WRB_REQ Writeback 1000
P_WRI_REQ WritebackInvalidate 1001
S_INV_REQ Invalidate 1010
S_CPB_REQ Copyback 1011
S_CPI_REQ CopybackInvalidate 1100
S_CPD_REQ CopybackToDiscard 1101
P_NCWR_REQ NonCachedWrite 1110
P_INT_REQ Interrupt 1111
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