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

部品番号

コンポーネント説明

メーカー

AM79C970

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

Advanced Micro Devices 

PRELIMINARY

AMD

Basic Burst Read Cycles

The PCnet-PCI controller provides a burst mode to read

data from the transmit buffer. The burst mode must be

enabled by setting BREADE in BCR18. All PCnet-PCI

controller burst read transfers are of the PCI command

type Memory Read Line (type15). AD[1:0] will both be

ZERO during the address phase indicating a linear burst

order. All four byte enable signals will be ZERO during

the data phase as the PCnet-PCI controller always

reads a full 32-bit word when in burst mode.

Figure 4 shows a typical burst read access. The PCnet-

PCI controller arbitrates for the bus, is granted access,

and reads four 32-bit words (DWORD) from system

memory and then releases the bus. All four data phases

in this example take two clock cycles each, which is de-

termined by the timing of TRDY.

CLK

1

2

3

4

5

6

7

8

9

10

11

12

13

FRAME

AD

ADDR

DATA

DATA

DATA

DATA

C/BE

1110

0000

PAR

PAR

PAR

PAR

PAR

PAR

IRDY

TRDY

DEVSEL

REQ

GNT

DEVSEL is sampled by the PCnet-PCI controller.

Figure 4. Burst Read Cycles

18220C-6

Am79C970

1-891

Share Link: