AR8327-AL1A-R datasheet(53/394 Pages) ETC2

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Atheros Communications, Inc.

AR8327/AR8327N Seven-port Gigabit Ethernet

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2.19.4

ARP ENTRY

The HNAT module supports 128 entries in the ARP table. The ARP table can be maintained by CPU. It

also can be automatically learned or aged by hardware through monitoring the ARP packets. This

table is used for Router function. The format of ARP table is shown below.

2.20 IEEE 802.3az and Energy Efficient Ethernet

IEEE 802.3az provides a mechanism to greatly save the power consumption between data packets

burst. The link partners enter Low Power Idle state by sending short refresh signals to maintain the

link.

There are two operating states, Active state for normal data transfer, and Low-power state between the

data packet bursts.

In the low-power state, the AR8327 shuts off most of the analog and digital blocks to conserve energy.

Due to the bursty traffic nature of Ethernet, system will stay in low-power mode in the most of time,

thus the power saving can be more than 90%.

At the link start up, both link partners exchange information via auto negotiation to determine if both

parties are capable of entering LPI mode.

Legacy Ethernet products are supported, and this is made transparent to the user.

Table 2-37.

ARP Entry

Bit

Name

Description

111

IP_VER

1’b1: IPv6

1’b0: IPv4

110:108

AGING_FLAG

3'h7: static

3'h1~6: valid & dynamic

3'h0: invalid

107

PPPOE EN

1'b1: add or change PPPoE header

106:103

PPPOE INDEX

PPPoE session id index, for change session or add PPPoE header.

102

CNT EN

1'b1: frame match this entry should be added to counter

101:98

CNT INDEX

Counter index to select counter.

97:96

ACTION

2'b00: Mirror

2'b01: Redirect

2'b10: Copy

2'b11: Forward

CPU ADDR

1'b1: this entry is for router address frame should be redirect to cpu. Normal

frame, not management

94:92

SPORT NUM

When doing ARP lookup, to determine destination port number

When doing source check, compare to frame SP.

91:83

VID OFFSET

Offset of VID to vid_low, vid_low+offset used to change frame VID

82:80

ROUTER MAC

INDEX

Index in router mac table

79:32

MAC ADDR

When doing ARP lookup, used to change frame DA

When doing source check, compare to frame SA

31:0

IP ADDR

When doing ARP lookup, compare to frame DIP

When doing source check, compare to frame SIP

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