RIVA128ZX datasheet(19/85 Pages) STMICROELECTRONICS

19 / 85 page

128-BIT 3D MULTIMEDIA ACCELERATOR

RIVA128ZX

19/85

Figure 8.

2X Read data, no delay

Figure 8 shows 32 bytes being transferred during 4 clocks (compared with 16 bytes in AGP 1x mode). The

control signals are identical. The AGPAD_STBx signal has been added when data is transferred at 8

bytes per PCICLK period. AGPAD_STBx represents AGPAD_STB0 and AGPAD_STB1 and are used

by the 2X interface logic to indicate when valid data is present on the AD bus. The control logic (PCITRDY#

in this case) indicates when data can be used by the target.

Figure 9.

2X Back to back read data, no delay

Figure 9 shows back to back 8 byte read transactions. AGPST[2:0] are shown toggling between “000”and

“001” to illustrate that they are actually changing. However, they are not required to change between high

and low priority to do back to back transactions. In this diagram, PCITRDY# is asserted on each clock

since a new transaction starts on each clock.

00x

xxx

PCICLK

PCIAD[31:0]

AGPADSTBx

AGPRBF#

PCITRDY#

PCIREQ#

PCIGNT#

AGPST[2:0]

123

456

000

001

000

001

000

001

000

001

+1 H5 +1

H4 +1

+L7

L8 +1 H6 +1 L9 +1

PCICLK

PCIAD[31:0]

AGPADSTBx

AGPRBF#

PCITRDY#

PCIGNT#

AGPST[2:0]

123456

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