TNETX15AE datasheet(6/78 Pages) TI

6 / 78 page

TNETX15AE

ADDRESS-LOOKUP DEVICE

SPWS041A – AUGUST 1997 – REVISED OCTOBER 1997

POST OFFICE BOX 655303

• DALLAS, TEXAS 75265

Terminal Functions

EAM interface

TERMINAL

I/O

DESCRIPTION

NAME

NO.

I/O

DESCRIPTION

†

External address match single-/multiple-port routing code select. When EAM15 is high, the EAM-interface terminals

contain a single-port routing code. When EAM15 is low, the EAM-interface terminals contain a multiple-port routing

code.

External address match port routing code select. When EAM15 is high, the EAM14–EAM0 terminals are placed in

the single-port mode. In this mode EAM14–EAM0 terminals encode a single port to which the frame is routed.

EAM14–EAM5 are don’t-care bits and are set to 0. The single-port codes (EAM15–EAM0 terminals) are shown in

the following:

EAM15†

EAM14

EAM13

EAM12

EAM11

EAM10

EAM09

EAM08

106

105

104

103

102

101

TNETX3150/TNETX3100

EAM15–EAM0

Port 00 (uplink)

Port 01

Port 02

Port 03

Port 04

Port 05

Port 06

Port 07

Port 08

Port 09

Port 10

Port 11

Port 12

Port 13

Port 14

Reserved

No-operation code

EAM07

EAM06

EAM05

EAM04

EAM03

EAM02

EAM01

EAM00‡

The no-operation code signals that the EAM device does not take part in forwarding decisions on this packet. The

TNETX15AE does not put out this code in normal operations. To successfully disable the TNETX15AE, it is reset and

not started. This causes the EAM interface to float, and external pullup resistors on EAM15 and EAM04 (minimally)

to supply the no-operation code to the TNETX3150/TNETX3150A/TNETX3100 device. Erratic operation occurs if the

TNETX3150/TNETX3150A/TNETX3100 address matching is not enabled when the TNETX15AE is disabled. The

TNETX15AE, when enabled, overrides the operations of the TNETX3150/TNETX3150A/TNETX3100 matching

circuitry; but, it is strongly advised to disable the TNETX3150/TNETX3150A/TNETX3100 address matching if the

TNETX15AE is active. This prevents two logic blocks from attempting to control port suspension and other functions.

When EAM15 is low, the EAM14–EAM0 terminals encode the multiple ports to which the data frame is routed. Each

bit on the EAM14–EAM0 bus is coded as follows:

– 1 on the bit signifies that the data frame is routed to that port.

– 0 on the bit signifies that the data frame is not routed to that port.

Terminal number assignments have a one-to-one correspondence to the port numbers as shown in the following:

EAM Bus Bit

Port Number

For example, to multicast a frame to ports 08, 05, 02, and 00 a multiport code of 0000 0001 0010 0101 or 0x0125

is sent.

All multicast packets and unknown unicast packets are forwarded by multiport code (EAM15 = 0) even if only one

bit is set.

To discard a frame, a code of 0x0000 is output (multiple routing code with no ports selected):

EAM14–EAM0

TNETX3150/TNETX3100

Discard frame

0 0

0 0 0 0 0 0

0 0 0

† Most-significant bit

‡ Least-significant bit

TNETX15AE 数据表(PDF) 6 Page - Texas Instruments

TNETX15AE 数据表(HTML) 6 Page - Texas Instruments

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