TNETX15VE datasheet(50/113 Pages) TI1

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TNETX15VE

VLAN-ENGINE ADDRESS-LOOKUP DEVICE

SPWS028B – APRIL 1997 – REVISED SEPTEMBER 1997

POST OFFICE BOX 655303

• DALLAS, TEXAS 75265

PRINCIPLES OF OPERATION

The purpose of this section is to assist in the development of management operational code for the

TNETX15VE. Management operational code is drastically simplified when using the TNETX15VE since it is

designed to operate without the need for a management CPU. Many of the functions that previously were

performed by a CPU are now integrated on the TNETX15VE.

This section discusses the following topics:

• AbackgroundontheTNETX15VEarchitecture,includingthedata-storagealgorithmandthearbitration

between logic operations

• How to access the TNETX15VE registers through the DIO interface, and how these registers can be

used to access the internal/external SRAM, the EEPROM, and any MII-managed devices

• How to access the TNETX15VE through the DIO interface and through a hardware reset, and what

steps are needed to bring the TNETX15VE to an operational state

• How to use the logic operations to perform management-based lookups, adds, and deletions, and how

to set the forwarding option for VLANs.

• How to use the TNETX15VE interrupt support to create event-driven management operational code.

internal operation

This section describes the TNETX15VE hardware and how it affects the programmer and the

TNETX3150/TNETX3150A performance. The functionality described in this section is transparent to the user,

but it is included to help the user become familiar with the TNETX15VE architecture and how it interfaces to the

TNETX3150/TNETX3150A device. Refer to the latest TNETX3150/TNETX3150A documentation for additional

information.

EAM codings and in-order broadcasts (IOB)

The TNETX15VE uses two styles of EAM codings – single-port codes and multiple-port codings. The

TNETX3150/TNETX3150A treats these two types of coding differently.

Single-port codings are those that forward frames to a single port. The TNETX3150/TNETX3150A queues

these frames to the port queue.

Multiple-port codings forward frames to multiple ports. The TNETX3150/TNETX3150A creates an IOB list

structure to queue this frame to multiple-port queues. IOB lists use more bandwidth than a regular list because

IOB lists require the use of an extra 64-byte buffer to contain all queue pointers for other ports. If 64-byte frames

are sent to multiple ports, IOB structures can then use much of the TNETX3150/TNETX3150A’s available

bandwidth.

The TNETX15VE uses single-port codings when possible, to maximize performance. The TNETX15VE

inspects all multiple-port codings after masking by the VLAN vector of source port, removal of the source port,

and removal of TX-blocked ports to determine if they can be replaced by a single-port coding. If this is possible,

then The TNETX15VE outputs the single-port coding.

For a more complete description of IOB lists, refer to the latest TNETX3150/TNETX3150A specification.

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