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BUS OVERVIEW
later time; a retry response, implying that the transaction should be retried; or a hard error
response.
HITM# overrides DEFER# to determine the response type. DEFER# may still affect a locked
operation. See Chapter 5, Bus Transactions and Operations for details.
The requesting agent observes HIT#, HITM#, and DEFER# to determine the line's final state in
its cache. DEFER# inactive enables the requesting agent to complete the transaction in order and
make the transition to the final cache state. A transaction with DEFER# active (and HITM# in-
active) can be completed with a deferred reply transaction (and a delayed transition to final
cache state) or can be retried.
3.4.6.
Response Signals
The response signal group (see Table 3-14) provides response information to the requesting
agent in the Response Phase. The Response Phase of a transaction occurs after the Snoop Phase
of the same transaction, and after the Response Phase of a previous transaction. Also, if the
transaction includes a data transfer, the data transfer of a previous transaction must be complete
before the Response Phase for the new transaction is entered.
Type
Response Status
Response Parity
Target Ready (for writes)
Requests initiated in the Request Phase enter the In-order Queue, which is maintained by every
agent. The response agent is the agent responsible for completing the transaction at the top of
the In-order Queue. The response agent is the agent addressed by the transaction.
For write transactions, TRDY# is asserted by the response agent to indicate that it is ready to
accept write or writeback data. For write transactions with an implicit writeback, TRDY#
is asserted twice, first for the write data transfer and then again for the implicit writeback
data transfer.
The response agent asserts RS[2:0]# to indicate one of the valid transaction responses indicated
in Table 3-15.
3-20
Table 3-14. Response Signals
Signal Names
Number
RS[2:0]#
RSP#
TRDY#
3
1
1
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