Signal Description

R

2.4.4AGP Strobes Signals

Signal Name

Type

Description

 

 

 

AD_STB0

I/O

Address/Data Bus Strobe-0:This signal provides timing for 2x and 4x

 

(s/t/s)

data on AD[15:0] and the C/BE[1:0]# signals. The agent that is providing

 

AGP

the data drives this signal.

 

 

 

AD_STB0#

I/O

Address/Data Bus Strobe-0 Compliment: Differential strobe pair that

 

(s/t/s)

provides timing information for the AD[15:0] and C/BE[1:0]# signals. The

 

AGP

agent that is providing the data drives this signal.

 

 

 

AD_STB1

I/O

Address/Data Bus Strobe-1:This signal provides timing for 2x- and 4x-

 

(s/t/s)

clocked data on AD[31:16] and C/BE[3:2]# signals. The agent that is

 

AGP

providing the data drives this signal.

 

 

 

AD_STB1#

I/O

Address/Data Bus Strobe-1 Compliment: The differential compliment

 

(s/t/s)

to the AD_STB1 signal. It is used to provide timing for 4x-clocked data.

 

AGP

 

 

 

 

SB_STB

I

Sideband Strobe: This signal provides timing for 2x- and 4x- clocked

 

AGP

data on the SBA[7:0] bus. It is driven by the AGP master after the system

 

 

has been configured for 2x- or 4x- clocked sideband address delivery.

 

 

 

SB_STB#

I

Sideband Strobe Compliment: SB_STB# is the differential compliment

 

AGP

to the SB_STB signal. It is used to provide timing for 4x-clocked data.

 

 

 

2.4.5AGP/PCI Signals

For transactions on the AGP interface carried using AGP FRAME# protocol, these signals operate similar to their semantics in the PCI 2.1 specification the exact role of all AGP FRAME# signals are defined below.

Signal Name

Type

Description

 

 

 

G_FRAME#

I/O

FRAME: During FRAME# Operations, G_FRAME# is an output when the

 

s/t/s

MCH acts as an initiator on the AGP Interface.

 

AGP

 

 

 

 

G_IRDY#

I/O

Initiator Ready#: This signal indicates the AGP compliant master is

 

s/t/s

ready to provide all write data for the current transaction. Once G_IRDY#

 

AGP

is asserted for a write operation, the master is not allowed to insert wait

 

 

states. The master is never allowed to insert a wait state during the initial

 

 

data transfer (32 bytes) of a write transaction. However, it may insert wait

 

 

states after each 32-byte block is transferred.

 

 

 

G_TRDY#

I/O

Target Ready: This signal indicates the AGP compliant target is ready to

 

s/t/s

provide read data for the entire transaction (when the transfer size is less

 

AGP

than or equal to 32 bytes) or is ready to transfer the initial or subsequent

 

 

block (32 bytes) of data when the transfer size is greater than 32 bytes.

 

 

The target is allowed to insert wait states after each block (32 bytes) is

 

 

transferred on write transactions.

 

 

 

G_STOP#

I/O

STOP: G_STOP Is an input when the MCH acts as a FRAME#-based

 

s/t/s

AGP initiator and an output when the MCH acts as a FRAME#-based

 

AGP

AGP target. G_STOP# is used for disconnect, retry, and abort

 

 

sequences on the AGP interface.

 

 

 

26

Intel® 82845 MCH for SDR Datasheet

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Intel 845 manual AGP Strobes Signals, 5 AGP/PCI Signals