TNETX4090 datasheet(55/78 Pages) TI1

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TNETX4090

ThunderSWITCH II™ 9-PORT 100-/1000-MBIT/S ETHERNET™ SWITCH

SPWS044E – DECEMBER 1997 – REVISED AUGUST 1999

POST OFFICE BOX 655303

• DALLAS, TEXAS 75265

port trunking example

This example shows how to set up the TNETX4090 to support two port trunks. The first trunk group consists

of ports 1, 3, 5, and 7 (see Table 21); the second trunk group consists of ports 0, 2, and 6 (see Table 22).

Table 21. Trunk Group 0 Port Membership (Trunk0Ports Register)

PORT

Table 22. Trunk Group 1 Port Membership (Trunk1Ports Register)

PORT

The TrunkMapx registers are used to control the distribution of traffic across the ports within a trunk group. In

this example, the traffic for trunk group 0 has been equally distributed 25% (this assumes that bits 3–1 of the

MAC addresses are random enough to give an even distribution) for each of the four ports in the trunk. For any

given source and destination address pair, the traffic always uses the same port within the trunk. This ensures

that packets do not get disordered on the trunk ports. Note that, since port 4 is not a member of any port trunk

group, all the entries for this port have been set to 1. In fact, functionally, this can be thought of as a single port

trunk.

Table 23. TrunkMapx Register Settings (for Traffic Distribution on Trunk Groups 0 and 1)

MAP

TRUNK PORT

INDEX

extended port awareness

When the port routing code is derived from an xportcode field, which has its most significant bit set (1xxxxx)

indicating a port on an external crossbar matrix connected to port 8, the port-8 bit in the port routing code is set,

and the five least significant bits of xportcode are used to create the pretag transmitted with the frame.

When bit 8 of the port routing code is set by a portvector field, the xroutecode field associated with the portvector

is used to create the pretag transmitted with the frame (either directly if xroutecode is in the range

000000–010000, or indirectly via a lookup in the XMultiGroup17–XMulUGroup63 registers if xroutecode is in

the range 010001–111111).

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