TNETX3150A datasheet(2/113 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

description (continued)

All 15 ports are full-duplex capable. With full-duplex capability, ports 03–14 can support 20-Mbit/s connections

and ports 01–02 can support 200-Mbit/s connections to desktops or high-speed servers through external

physical (PHY) layers. The uplink port 00 can provide a 400-Mbit/s (200 Mbit/s full duplex) connection for either

external-switching fabric, external routing engine, or high-speed stacking links. ThunderSWITCH is capable of

supporting VLAN for workgroup and segment-switching applications.

Data received from the media-access controller (MAC) interface is buffered in the RX FIFO before storage in

external buffer memory under control of the queue management (QM) logic. Both QM and MAC blocks apply

round-robin arbitration to maintain bandwidth and fast data transfer of the first-in, first-out (FIFO) subsystem

without contention.

The TNETX3150/TNETX3150A has three modes for making forwarding decisions: internal single-address

compare, external address match (EAM) interface, and frame tagging on the uplink port. All the 10-Mbit/s ports

internally support switching a single MAC address per port. An EAM interface is supplied to support multiple

addresses per port. External-address-matching hardware is required to support multiple users on one port.

Ports 01 and 02 (10-/100-Mbit/s high-speed connection) are similarly restricted. The uplink port 00 does not

have any internal address register and can support multiple addresses.

Upon transmission, frame data is obtained from the buffer memory and buffered temporarily into the TX FIFO

before transmission on the relevant MAC port. If a collision occurs during transmission, data recovery and

retransmission occur from the TX FIFO.

Statistics for the Etherstat and RMON management-information base are independently collected for each of

the 15 ports. Access to the statistics counters is provided via the direct input/output (DIO) interface. The DIO

interface is intended only for configuration and monitoring operations.

The TNETX3150/TNETX3150A utilizes a standard 60-ns memory solution (EDO DRAM).The packet memory

has been implemented to effectively support both single-access operation and page-burst-access operation.

All DRAM buffer transfers are made within a page boundary, permitting fast-burst accesses. A high-memory

bandwidth is maintained, allowing all ports to be active without bottlenecking at the memory buffer. The

TNETX3150/TNETX3150A allows any port configuration, including those that may exceed the maximum

buffer-memory bandwidth. This can cause packets to be dropped. To avoid these conditions, the port

configurations should be restricted so that the maximum allowable bandwidth to external buffer memory is not

exceeded.

Packets are routed to local ports based on the destination MAC address. The cut-through feature enables

transmission on the destination port before complete reception of the frame, which reduces the overall switch

latency. The cut-through feature can be employed for all situations where the transmission port is slower or

equal to the data rate on the receiving port. 100 Mbit/s can cut through to another 100-Mbit/s port or a 10-Mbit/s

port. However, a 10-Mbit/s port cannot cut through to a 100-Mbit/s port. For this case, local cut-through is

automatically disabled to prevent underflow. The cut-through feature can be disabled by either the receiving port

or transmitting port, on a per-port basis, by setting the store-and-forward option bits in the port-control registers.

If the TNETX3150/TNETX3150A is operating in store-and-forward mode, the entire frame must be received

before it is transmitted to the destination port. This provides the ability to filter frames that contain errors. This

mode can be configured either by using the port control registers or is used automatically when transmitting from

a low-speed to a high-speed port, since cut-through is not possible in this case.

TNETX3150A 数据表(PDF) 2 Page - Texas Instruments

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