AM79C940 datasheet(21/144 Pages) AMD

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Am79C940

RXDAT Configuration

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.

RXCRS Configuration

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.

DXCVR

Disable Transceiver (Output)

An output from the MACE device to indicate the net-

work port in use, as programmed by the ASEL bit or the

PORTSEL [1–0] bits. The output is provided to allow

power down of an external DC-to-DC converter, typi-

cally used to provide the voltage requirements for an

external 10BASE2 transceiver.

When the Auto Select (ASEL) feature is enabled, the

state of the PORTSEL [1–0] bits is overridden, and the

network interface will be selected by the MACE device,

dependent only on the status of the 10BASE-T link. If

the link is active (LNKST pin driven LOW) the

10BASE-T port will be used as the active network inter-

face. If the link is inactive (LNKST pin pulled HIGH) the

AUI port will be used as the active network interface.

Auto Select will continue to operate even when the

SLEEP pin is asserted if the RWAKE bit has been set.

The AWAKE bit does not allow the Auto Select func-

tion, and only the receive section of 10BASE-T port will

be active (DXCVR = HIGH).

Active (HIGH) when either the 10BASE-T or DAI port

is selected. Inactive (LOW) when the AUI or GPSI port

is selected.

SLEEP

PORTSEL

[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)

SLEEP

PORTSEL

[1-0]

ENDPLSIO

Interface Description

Pin Function

Sleep Mode

High Impedance

1001

AUI

RXCRS Output

10BASE-T

RXCRS Output

DAI Port

RXCRS Output

GPSI

RXCRS Output

Status Disabled

High Impedance (Note 2)

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