82845MP Datasheet, PDF (28/157 Pages) Intel Corporation – Intel 845 Family Chipset-Mobile 82845MP/82845MZ Chipset Memory Controller Hub Mobile (MCH-M)

Intel^®82845MP/82845MZ Chipset-Mobile (MCH-M)
R
Signal Name
G_STOP#
G_DEVSEL#
G_REQ#
G_GNT#
G_AD[31:0]
G_CBE[3:0]#
Type
I/O
s/t/s
AGP
I/O
s/t/s
AGP
I
AGP
O
AGP
I/O
AGP
I/O
AGP
Description
G_STOP#: Stop
During PIPE# and SBA Operation: This signal is not used during PIPE# or SBA
operation.
During FRAME# Operation: G_STOP# is an input when the MCH-M acts as a
FRAME#-based AGP initiator and is an output when the MCH-M acts as a
FRAME#-based AGP target. G_STOP# is used for disconnect, retry, and abort
sequences on the AGP interface
G_ DEVSEL#: Device Select
During PIPE# and SBA Operation: This signal is not used during PIPE# or SBA
operation.
During FRAME# Operation: G_DEVSEL#, when asserted, indicates that a
FRAME#-based AGP target device has decoded its address as the target of the
current access. The MCH-M asserts G_DEVSEL# based on the SDRAM address
range being accessed by a PCI initiator. As an input, G_DEVSEL# indicates
whether the AGP master has recognized a PCI cycle to it.
G_REQ#: Request
During SBA Operation: This signal is not used during SBA operation.
During PIPE# and FRAME# Operation: G_REQ#, when asserted, indicates that
the AGP master is requesting use of the AGP interface to run a FRAME#- or
PIPE#-based operation.
G_GNT#: Grant
During SBA, PIPE# and FRAME# Operation: G_GNT#, along with the
information on the ST[2:0] signals (status bus), indicates how the AGP interface will
be used next. Refer to the AGP Interface Specification, Revision 2.0 for further
explanation of the ST[2:0] values and their meanings.
G_AD[31:0]: Address/Data Bus
During PIPE# and FRAME# Operation: The G_AD[31:0] signals are used to
transfer both address and data information on the AGP interface.
During SBA Operation: The G_AD[31:0] signals are used to transfer data on the
AGP interface.
Command/Byte Enable
During FRAME# Operation: During the address phase of a transaction, the
G_CBE[3:0]# signals define the bus command. During the data phase, the
G_CBE[3:0]# signals are used as byte enables. The byte enables determine which
byte lanes carry meaningful data. The commands issued on the G_CBE# signals
during FRAME#-based AGP transactions are the same G_CBE# command
described in the PCI 2.2 specification.
During PIPE# Operation: When an address is enqueued using PIPE#, the C/BE#
signals carry command information. Refer to the AGP 2.0 Interface Specification,
Revision 2.0 for the definition of these commands. The command encoding used
during PIPE#-based AGP is different than the command encoding used during
FRAME#-based AGP cycles (or standard PCI cycles on a PCI bus).
During SBA Operation: These signals are not used during SBA operation.
28
Datasheet
250687-002