TNETX3100 datasheet(18/80 Pages) TI1

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TNETX3100

ThunderSWITCH™ 10-PORT 10-/100-MBIT/S ETHERNET™ SWITCH

SPWS031D – JUNE 1997 – REVISED OCTOBER 1997

POST OFFICE BOX 655303

• DALLAS, TEXAS 75265

uplink RX posttagging to support an external routing engine (continued)

M00RXD3–

M00RXD0

M00RCLK

M00RXDV

Tag0

Tag1

Tag2

DA, SA, Data, CRC, Ethernet Frame

3-Nibble Tag Field Appended

to the End of the Ethernet

Frame Reception

Figure 4. Data Format for Uplink RX Frames

uplink frame RX routing via posttagging

The tag fields are coded as shown in Figure 5:

tag 0

BIT 3

BIT 2

BIT 1

BIT 0

Destination Port 04

10 Mbit/s

Destination Port 03

10 Mbit/s

Destination Port 02

10 Mbit/s

Destination Port 01

10/100 Mbit/s

tag 1

BIT 3

BIT 2

BIT 1

BIT 0

Destination Port 08

10 Mbit/s

Destination Port 07

10 Mbit/s

Destination Port 06

10 Mbit/s

Destination Port 05

10 Mbit/s

tag 2

BIT 3

BIT 2

BIT 1

BIT 0

Reserved

Destination Port 09

10 Mbit/s

Figure 5. Tag Field Coding

If only one bit is set in the destination-port field, the packet is a unicast. With tag 0 = 0000, tag 1 = 0100, and

tag 2 = 0000, the packet is unicast and destined for port 06.

If more than one bit is set, the packet is VLAN multicast. With tag 0 = 1010, and tag 1 = 1001, and tag 2 = 0001, the

packet is transmitted from ports 02, 04, 05, 08, and 09. This allows broadcast and multicast traffic to be limited in

supporting external VLANs.

If all bits are clear in the tags, the packet is invalid and is discarded.

100-Mbit/s MAC interfaces (port 01)

This port is identical to the uplink port (port 00) except that it does not support posttagging. The port provides the

pretag prior to TXEN going active. The tag is ignored by externally connected PHYs.

TNETX3100 Datasheet(PDF) 18 Page - Texas Instruments

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