The Data Phase Signal Group

Table 51-2 on page 1247 defines the signals used during the Data Phase of a transaction.

Table 51-2. Data Phase-related Signals
Signal(s)Description
DBSY#

Data Bus Busy. Asserted by the agent that will drive data on the data bus (i.e., the Response Agent on a read; the Request Agent on a write; the Snoop Agent on a snoop hit on modified line) to indicate that it is taking ownership of the Data Bus. DBSY# is deasserted at one of the following times:

  • In the same BCLK cycle wherein the final data is transferred.

  • One BCLK cycle after the final data is transferred (this is referred to as Relaxed deassertion of DBSY#).

DRDY#

Data Ready. Asserted by the agent sourcing data to indicate that valid data is being driven onto the Data Bus during the current BCLK cycle. If DRDY# is deasserted during the Data Phase, this indicates that the device sourcing the data will not present valid data during the current BCLK cycle.

D[63:0]#

The Data Bus. The eight data paths are used to transfer up to a qword on each falling-edge of the Data Strobes.

DBI[3:0]#The Data Bus Inversion signals. These signals are asserted by the device sourcing the data if the data was inverted before being driven (to conserve power). Refer to “The Data Bus Inversion Signals” on page 1125.
DSTBN[3:0]# and DSTBP[3:0]#The Data Strobe Signals are sourced by the same device that sources the data (hence the term source-synchronous strobes). The device receiving the data uses the falling-edge of the strobes to latch data into its receive buffers. Refer to “The Pentium® 4/M Data Delivery Method” on page 1123.
DP[3:0]#Data bus parity protection bits. Refer to “Data Bus Parity” on page 1270.

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