AM79C970 Просмотр технического описания (PDF) - Advanced Micro Devices

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AM79C970

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

Advanced Micro Devices 

AMD

PRELIMINARY

Preemption When FRAME is Asserted

The central arbiter can take GNT to the PCnet-PCI con-

troller away if the current bus operation takes too long.

This may happen e.g. when the PCnet-PCI controller

tries to fill the whole transmit FIFO and the target inserts

extra wait states for every data phase. When GNT is

taken away, the PCnet-PCI controller will finish the

current transfer and then immediately release the bus.

The Latency Timer in PCI configuration space of the

PCnet-PCI controller is always set to ZERO. The PCnet-

PCI controller will keep REQ asserted to regain bus

ownership as soon as possible.

CLK

1

2

3

4

5

6

7

8

9

FRAME

AD

ADDR DATA

DATA DATA

C/BE

0111

0000

PAR

PAR PAR

PAR PAR

IRDY

TRDY

DEVSEL

REQ

GNT

DEVSEL is sampled by the PCnet-PCI controller.

Figure 11. Preemption When FRAME is Asserted

18220C-13

1-898

Am79C970

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