AM79C940VCW datasheet(20/122 Pages) AMD

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AMD

Am79C940

TXEN/TXEN

Transmit Enable

(Output)

When the AUI port is selected (PORTSEL [1–0] = 00),

an output indicating that the AUI DO

± differential output

has valid Manchester encoded data is presented. When

the 10BASE-T port is selected (PORTSEL [1–0] = 01),

indicates that Manchester data is being output on the

TXD

±/TXP± complementary outputs. When the DAI

port is selected (PORTSEL [1–0] = 10), indicates that

Manchester data is being output on the DAI

port

TXDAT

± complementary outputs. When the GPSI port

is selected (PORTSEL [1–0] =11), indicates that NRZ

data is being output from the MAC core of the MACE de-

vice, to an external Manchester encoder/decoder, on

the TXDAT+ output. Active low when the DAI port is se-

lected, active high when the AUI, 10 BASE-T or GPSI is

selected. Operates at TTL levels.

RXDAT

Receive Data

(Input)

When the DAI port is selected (PORTSEL [1–0] = 10),

the Manchester encoded data input to the integrated

clock recovery and Manchester decoder of the MACE

device, from an external network transceiver. When the

GPSI port is selected (PORTSEL [1–0] =11), the NRZ

decoded data input to the MAC core of the MACE de-

vice, from an external Manchester encoder/decoder.

Operates at TTL levels.

RXCRS

Receive Carrier Sense

(Input/Output)

When the AUI port is selected (PORTSEL [1–0] = 00),

an output indicating that the DI

± input pair is receiving

valid Manchester encoded data from the external trans-

ceiver which meets the signal amplitude and pulse width

requirements. When the 10BASE-T port is selected

(PORTSEL [1–0] = 01), an output indicating that the

RXD

± input pair is receiving valid Manchester encoded

data from the twisted pair cable which meets the signal

amplitude and pulse width requirements. RXCRS will be

asserted high for the entire duration of the receive mes-

sage. When the DAI port is selected (PORTSEL [1–0] =

10), an input signaling the MACE device that a receive

carrier condition has been detected on the network, and

valid Manchester encoded data is being presented to

the MACE device on the RXDAT line. When the GPSI

port is selected (PORTSEL [1–0] = 11), an input signall-

ing the internal MAC core that valid NRZ data is being

presented on the RXDAT input. Operates at TTL levels.

TXEN/TXEN Configuration

PORTSEL

SLEEP

[1–0]

ENPLSIO

Interface Description

Pin Function

Sleep Mode

High Impedance

AUI

TXEN Output

10BASE-T

TXEN Output

DAI Port

TXEN Output

GPSI

TXEN Output

Status Disabled

High Impedance (Note 3)

Notes:

1. PORTSEL [1–0] and ENPLSIO are located in the PLS Configuration Control register (REG ADDR 14).

2. When the GPSI port is selected, TXEN should have an external pull-down attached (e.g. 3.3k

Ω) to ensure the output is held

inactivebefore ENPLSIO is set.

3. This pin should be externally terminated, if unused, to reduce power consumption.

RXDAT Configuration

PORTSEL

SLEEP

[1–0]

ENPLSIO

Interface Description

Pin Function

Sleep Mode

High Impedance

AUI

High Impedance (Note 2)

10BASE-T

High Impedance (Note 2)

DAI Port

RXDAT Input

GPSI

RXDAT Input

Status Disabled

High Impedance (Note 2)

Notes:

1. PORTSEL [1–0] and ENPLSIO are located in the PLS Configuration Control register (REG ADDR 14).

2. This pin should be externally terminated, if unused, to reduce power consumption.

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