TNETX15AE datasheet(18/78 Pages) TI

18 / 78 page

TNETX15AE

ADDRESS-LOOKUP DEVICE

SPWS041A – AUGUST 1997 – REVISED OCTOBER 1997

POST OFFICE BOX 655303

• DALLAS, TEXAS 75265

age-deletion time-select register, agingtimer at 0x02–0x03 (DIO)

BYTE 1

BYTE 0

BIT

Agingtimer

Initial values after reset

The agingtimer register is 16 bits wide and is used to control the aging process. There are two aging modes,

and the modes are selected according to the value of this register:

D When agingtimer is 0 or 0xFFFF, the TNETX15AE performs table-full aging. The TNETX15AE ages out the

oldest address when the lookup table becomes full.

D When agingtimer is not 0 or 0xFFFF, the TNETX15AE performs threshold aging. The value in the agingtimer

is the time threshold in seconds. All addresses that are older than this time are aged out.

Aging does not delete addresses that have been secured, and multicast addresses also are not aged. Aging

is disabled when the NAUTO bit in the control register is set. It is management’s responsibility in NAUTO mode

to manage the lookup table.

All bits in this register are read/writeable and default to 0x0 during reset. This field also is automatically loaded

from the EEPROM when the RESET terminal is asserted low or when LOAD in the control register is set to 1.

unknown unicast port-routing register, unkuniports at 0x04–0x05 (DIO)

BYTE 1

BYTE 0

BIT

Reserved

Unkuniports

Initial values after reset

The unkuniports register is used to route unicast frames whose destination address is not found within the

lookup table. Normally these frames are flooded to all ports except to the port that originated the frame. The

TNETX15AE uses the unkuniports register to route these frames to only selected ports. When the TNETX15AE

uses the unkuniports register for unicast flooding, it increments the unkunictr counter. The TNETX15AE masks

out the originating port when using this register. This prevents the attached switch device from forwarding the

frame to its originating port.

The bit numbers in this register have a one-to-one correspondence with the attached switch-device port number.

This register is readable/writeable and is auto-loaded from the EEPROM when the RESET terminal is asserted

low or when LOAD in the control register is set.

TNETX15AE 数据表(PDF) 18 Page - Texas Instruments

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