TNETX3150 datasheet(24/113 Pages) TI1

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TNETX3150/TNETX3150A

ThunderSWITCH™ 15-PORT 10-/100-MBIT/S ETHERNET™ SWITCH

SPWS027F – FEBRUARY 1997 – REVISED SEPTEMBER 1997

POST OFFICE BOX 655303

• DALLAS, TEXAS 75265

uplink TX pretagging (continued)

Table 1. Source Port Number Codes

SOURCE

PORT NUMBER

PORT

0000

Reserved

0001

Port 01 (10/100 Mbit/s)

0010

Port 02 (10/100 Mbit/s)

0011

Port 03 (10 Mbit/s)

0100

Port 04 (10 Mbit/s)

0101

Port 05 (10 Mbit/s)

0110

Port 06 (10 Mbit/s)

0111

Port 07 (10 Mbit/s)

1000

Port 08 (10 Mbit/s)

1001

Port 09 (10 Mbit/s)

1010

Port 10 (10 Mbit/s)

1011

Port 11 (10 Mbit/s)

1100

Port 12 (10 Mbit/s)

1101

Port 13 (10 Mbit/s)

1110

Port 14 (10 Mbit/s)

1111

Reserved

Port 00, when operated at 100-Mbit/s (M00UPLINK = 1), provides a tag nibble one cycle before M00TXEN is

asserted. A preamble is provided on this port when operated at 100 Mbit/s. The nibble format is shown in

Table 1.

uplink RX pretagging

When port 00 (uplink) is operated in 200-Mbit/s mode, a pretag can be placed one cycle before MRXDV goes

high for the frame. This pretag is not operated on internally by the TNETX3150/TNETX3150A. The tag is passed

to the DRAM interface, where it appears on bits 31–28 of the forward pointer of the buffer transfer for the frame

received on the uplink. Tag data that is applied to M00RXD0–M00RXD3 is passed, and tag data that is applied

on M00RXD4–M00RXD7 is ignored. This allows an upstream device, connected to the uplink, to pass

information through the TNETX3150/TNETX3150A to the DRAM bus where an external lookup device can

operate on that information. It also enables two ThunderSWITCH devices, when cascaded, to pass

frame-source port information from the receiving TNETX3150/TNETX3150A to the cascaded external

address-lookup devices. See Figure 6.

The pretag is qualified with the channel number of the port that received the frame. Only pretags for frames

whose port number is 00 are valid. For frames that are not received on the uplink (port 00), the pretag is zero.

A pretag received on the uplink (port 00) is retained for the duration of the frame.

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