Hub Datasheet

Intel
®
E7505 Chipset MCH Datasheet 33
Signal Description
2.6 AGP Interface Signals
2.6.1 AGP Arbitration Signals
Table 2-6. AGP Arbitration Signals
Signal Name Type Description
GREQ# (2.0)
GREQ (3.0)
I
AGP
Request: This signal is the output of the AGP device used to request access to
the bus to initiate a PCI (GFRAME(#)) or AGP (PIPE#) request. This signal is
not required to initiate an AGP request via SBA.
GGNT# (2.0)
GGNT (3.0)
O
AGP
Grant: This signal is the output of the MCH either granting the bus to the AGP
device to initiate a GFRAME(#) or PIPE(#) access (in response to GREQ(#)
active) or to indicate that data is to be transferred for a previously enqueued
AGP transaction. ST[2:0] indicates the purpose of the grant.
ST[2:0]
O
AGP
Status: This signal provides information from the arbiter to an AGP Master on
what it may do. ST[2:0] only have meaning to the master when its GGNT(#) is
asserted. When GGNT(#) is deasserted these signals have no meaning and
must be ignored.
ST[2:0] are always an output from the MCH and an input to the master.
Encoding Meaning
000
Previously requested low priority read data (Async read for
AGP 3.0 signaling mode) is being returned to the master
001
Previously requested high priority read data is being returned to
the master. Reserved in AGP 3.0 signaling mode
010
The master is to provide low priority write data (Async Write for
AGP 3.0 signaling mode) for a previously queued write
command
011
The master is to provide high priority write data for a previously
queued write command. Reserved in AGP 3.0 signaling mode.
100
Previously requested isochronous read data is being returned
to the master. AGP 3.0 signaling mode only.
101
The master is to provide isochronous write data for a previously
queued write command. AGP 3.0 signaling mode only.
110 Calibration cycle. AGP 3.0 signaling mode only.
111
The master has been given permission to start a bus
transaction. The master may queue AGP requests by asserting
PIPE# (4x mode) or start a PCI transaction by asserting
GFRAME(#).