IP175DLF datasheet(49/145 Pages) ETC

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IP175DLF

Datasheet

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August 22, 2014

IP175DLF-DS-R10.1

buckets with four entries in each bucket. Each bucket is located through its respective hash key,

calculated from MAC and FID by using XOR algorithm. It is possible that multiple MAC addresses index to

the same bucket, term as collision. IP175DLF provides four entries within each buck for reducing collision

rate. Finally, the 11-bit hash index mapping to MAC table consist of three parameters: multicast address

bit, hash key and entry number. The MSB of hash index distinguishes multicast address from MAC

addresses. The least two significant bit in hash index indicates entry number. The other bit is hash key

which calculated from MAC and FID using XOR algorithm. In IP175DLF the formula of hash index is

computed based on table structure. The user can set AT_STR bit to configure table structure. The 11-bit

hash index is computed as following:

AT_STR=0 (2K unicast table)

Hash Index = { XOR( {2'b00,FID,MAC[47:45]}, MAC[44:36], MAC[35:27], MAC[26:18], MAC[17:9],

MAC[8:0] ), Entry Number }

AT_STR=1 (1K unicast table and 1K multicast table)

Hash Index = {Multicast Address Bit, XOR( {4'h0,FID}, MAC[47:40], MAC[39:32], MAC[31:24],

MAC[23:16], MAC[15:8], MAC[7:0] ), Entry Number }

3.9.1

Entry Content

Entry content in MAC table contains the forwarding information for a specific MAC address. This table

content is automatically updated by learning process and can directly access from the CPU through

Address Table Access register (see MII register 21.14-19).

The contents are described in Table 3, Table 4 and Table 5.

MII Register

Name

Description

21.15

MAC_ADDR[15:0]

MAC address[15:0]

21.16

MAC_ADDR[31:16]

MAC address[31:16]

21.17

MAC_ADDR[47:32]

MAC address[47:32]

21.18[15:14]

FILTER_INFO

Filter information:

2’b00: reserved

2’b01: discard frame if frame’s SMAC match MAC address

2’b10: ignore VLAN member set

2’b11: copy frame to mirror port if frame’s DMAC match MAC

address

21.18[13:10]

PRI_INFO

Priority information: To assign queue number for frames with match

MAC table entry. The information is divided two parts: match

condition and its action.

Match Condition (21.18[13:12]):

2’b00: reserved

2’b01: match DMAC (Destination MAC Address)

2’b10: match SMAC (Source MAC Address)

2’b11: match DMAC or SMAC

Action (21.18[11:10]):

Assign to Queue 0

Assign to Queue 1

Assign to Queue 2

Assign to Queue 3

21.18[9:6]

FID

4-bit FID

21.18[5:3]

PORT_ID

Port ID:

3’b000: discard frame if frame’s DMAC match MAC address

3’b001- 3’b110: port ID

3’b111: reserved

21.18[2:0]

AGE

Age time: If this field is set all zero, it indicates the corresponding

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