AM79C970 データシートの表示（PDF） - Advanced Micro Devices

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AM79C970

PCnet™-PCI Single-Chip Ethernet Controller for PCI Local Bus

Advanced Micro Devices 

PRELIMINARY

AMD

Master Initiated Termination

There are three scenarios besides normal completion of

a transaction where the PCnet-PCI controller will termi-

nate the cycles it produces on the PCI bus.

Preemption When FRAME is Deasserted

The PCnet-PCI controller will generate multiple address

phases during a single bus ownership period when it is

accessing the initialization block, the descriptor ring

entries and the data buffers in main memory. FRAME is

deasserted in between two address phases. While

FRAME is deasserted, the central arbiter can remove

GNT to the PCnet-PCI controller at any time to service

another master. When GNT is removed, the PCnet-PCI

controller will finish the current transfer and then release

the bus. It will keep REQ asserted to regain bus owner-

ship as soon as possible.

CLK

1

2

3

4

5

6

7

8

FRAME

AD

ADDR DATA

C/BE

0111 BE's

PAR

PAR PAR

IRDY

TRDY

DEVSEL

REQ

GNT

DEVSEL is sampled by the PCnet-PCI controller.

Figure 10. Preemption When FRAME is Deasserted

18220C-12

Am79C970

1-897

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