TNETX3150 datasheet(23/113 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 port interface (port 00)

The uplink can be used as a 15th 10-/100-Mbit/s switched port, even though no address compare register exists

for it. Packets are switched to it by default if the destination address is not matched to any of the other 14 ports.

The uplink port implementation is similar to the 10-/100-Mbit/s port described previously. However, the uplink

port is capable of 200 Mbit/s by using byte-wide transfers rather than nibble transfers. This 200-Mbit/s wide

uplink mode is selected by asserting M00UPLINK low.

uplink multiplexing operation

With M00UPLINK set low, all packets are sent to the uplink port by default. Broadcast and unicast traffic received

on ports 01–14 are treated similarly (forwarded to the uplink only, if no local addressing is enabled). Identification

of broadcast traffic is retained for statistical counting purposes. The address-compare disable option bits

(ADRDIS) (port control register) are set for all ports except port 00. Local-address comparison is possible by

clearing the ADRDIS bits for the ports that take part in address comparison. Alternatively, the EAM interface

can be used in the normal manner. Setting M00UPLINK low also selects store-and-forward operation on all ports

to prevent data underflows and to permit frame-error filtering. If local-frame switching is employed, clearing the

relevant STFORRX bits for ports 01–14 and ensuring both STFORRX and STFORTX bits are set for port 00

(uplink), improves performance by permitting cut-through where possible (store-and-forward operation permits

frame-error filtering, but cut-through does not).

uplink TX pretagging

When M00UPLINK is low, it is desirable to have an indication of which port received the frame. This permits

an address lookup device to be connected to the uplink port, allowing incorporation of the

TNETX3150/TNETX3150A into a larger switch fabric. The TNETX3150/TNETX3150A provides one byte of

information (to identify the source port) on the Mll data terminals before M00TXEN is asserted. See Figure 5.

M00TCLK

M00TXD7–M00TXD0

M00COL

Don’t Care

TAG

DA, SA, Data, CRC

M00TXEN

Don’t Care

1-Byte Tag Field Added to Frame

No Preamble Transmitted at 200 Mbit/s.

Figure 5. Multiplex Operation for Uplink-Port Transmit Frames

The pretag byte format is as follows:

BIT 7

BIT 4

BIT 3

BIT 2

BIT 1

BIT 0

Reserved

Source Port Number

The source port number is coded as shown in Table 1.

TNETX3150 数据表(PDF) 23 Page - Texas Instruments

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