TNETX3150 datasheet(71/113 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

address compare unit (continued)

MUX

Address Register

Compare

Encoder

Matched Address Signal

Load Register

Ethernet Address

48 Bits

Address Match Bus

Destination Channel Address

Figure 29. Address Compare Logic

port address register configuration

The port addresses can be assigned explicitly or dynamically. An address is explicitly assigned by writing it to

the port address registers via the DIO interface. An address is assigned dynamically by the

TNETX3150/TNETX3150A hardware, loading the register from the source address field of the received frames.

If the port is in secured mode, the address is loaded only once from the first frame. In unsecured mode, the

address is updated on every frame received.

The uplink port (port 00) does not have a port address register. If it receives a frame with a source address

securely assigned to another port, the uplink either disables or continues to operate, depending on the SECDIS

bit. When SECDIS is set, the port disables on receipt of a securely assigned address. When SECDIS is reset,

the port continues to operate. Port suspension, due to address mismatch, is not supported on the uplink. Since

no port address exists, suspension on a multiple-address port is not desirable.

IOB operation

This mode of handling broadcast traffic is selected by setting the IOBMOD bit in the system control register. IOB

handling ensures that frames that are broadcast follow the strict order in which they were received.

When a multicast frame is detected in IOB mode, the reception continues in the same manner as for a normal

store-and-forward frame. The buffers comprising the frame are linked in the receive queue.

When the end of frame is detected, an additional buffer is linked to the end of the receive queue. This buffer

is similar in size to a normal data buffer, but contains indexed queue information rather than frame data. To

distinguish between the types of buffers, bit 23 of the tag field is set.

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