AM79C974 datasheet(34/153 Pages) AMD

Part #	AM79C974

Description	PCnetTM-SCSI Combination Ethernet and SCSI Controller for PCI Systems

PDF	153 Pages

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Manufacturer	AMD [Advanced Micro Devices]

Direct Link	http://www.amd.com

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AMD

P R E L I M I N A R Y

Am79C974

Basic Non-Burst Write

All Am79C974 controller non-burst write accesses are

of the PCI command type Memory Write (type 7).

Figure 8 shows two non-burst write access within one

arbitration cycle. The Am79C974 controller will drop

FRAME between two consecutive non-burst write cy-

cles. The Am79C974 controller will re-request the bus

immediately if it is preempted before starting the second

access. The example below shows an extended cycle

for the first access. The target asserts

DEVSEL 2 clock

cycles after the address phase (

FRAME asserted) and

adds one extra wait state by asserting

TRDY only on

clock 7. The second write cycle in the example shows a

ZERO wait state access.

18681A-12

FRAME

CLK

IRDY

TRDY

DEVSEL

REQ

GNT

12345678

ADDR

BE's

0111

PAR

DATA

ADDR

DATA

BE's

0111

PAR

DEVSEL is sampled by the Am79C974 controller.

Figure 8. Non-Burst Write Cycles With and Without Wait States

AM79C974 Datasheet(PDF) 34 Page - Advanced Micro Devices

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