AM79C976 datasheet(26/309 Pages) AMD

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Am79C976

8/01/00

P R E L I M INARY

PME

Power Management Event

Output, Open Drain

PME is an output that can be used to indicate that a

power management event (a Magic Packet, an OnNow

pattern match, or a change in link state) has been de-

tected. The PME pin is asserted when either:

1. PME_STATUS and PME_EN are both 1,

2. PME_EN_OVR and MPMAT are both 1, or

3. PME_EN_OVR and LCDET are both 1.

The PME signal is asynchronous with respect to the

PCI clock.

Board Interface

Note: Before programming the LED pins, see the de-

scription of LEDPE in BCR2, bit 12.

LED0

Output

This output is designed to directly drive an LED. By de-

fault, LED0 indicates an active link connection. This pin

can also be programmed to indicate other network sta-

tus (see BCR4). The LED0 pin polarity is programma-

ble, but by default it is active LOW. When the LED0 pin

polarity is programmed to active LOW, the output is an

open drain driver. When the LED0 pin polarity is pro-

grammed to active HIGH, the output is a totem pole

driver.

Note: The LED0 pin is multiplexed with the EEDI pin.

LED1

Output

This output is designed to directly drive an LED. By de-

fault, LED1 indicates receive or transmit activity on the

network. This pin can also be programmed to indicate

other network status (see BCR5). The LED1 pin polar-

ity is programmable, but by default, it is active LOW.

When the LED1 pin polarity is programmed to active

LOW, the output is an open drain driver. When the

LED1 pin polarity is programmed to active HIGH, the

output is a totem pole driver.

Note: The LED1 pin is multiplexed with the EESK pin.

LED2

Output

This output is designed to directly drive an LED. By de-

fault, LED2 indicates that the network bit rate is 100

Mb/s. This pin can also be programmed to indicate var-

ious network status (see BCR6). The LED2 pin polarity

is programmable, but by default it is active LOW. When

the LED2 pin polarity is programmed to active LOW, the

output is an open drain driver. When the LED2 pin po-

larity is programmed to active HIGH, the output is a

totem pole driver.

Note: The LED2 pin is multiplexed with the RXFRTGE

pin.

LED3

Output

This output is designed to directly drive an LED. By de-

fault, LED3 indicates that a collision has occurred. This

pin can also be programmed to indicate other network

status (see BCR7). The LED3 pin polarity is program-

mable, but by default it is active LOW. When the LED3

pin polarity is programmed to active LOW, the output is

an open drain driver. When the LED3 pin polarity is pro-

grammed to active HIGH, the output is a totem pole

driver.

Special attention must be given to the external circuitry

attached to this pin. When this pin is used to drive an

LED while an EEPROM is used in the system, then

buffering may be required between the LED3 pin and

the LED circuit. If an LED circuit were directly attached

to this pin, it may create an IOL requirement that could

not be met by the serial EEPROM attached to this pin.

If no EEPROM is included in the system design or low

current LEDs are used, then the LED3 signal may be

directly connected to an LED without buffering. In any

case, if an EEPROM is present, there must be a pull-up

resistor connected to this pin (10 k

W should be ade-

quate). For more details regarding LED connection,

see the section on LED Support.

Note: The LED3 pin is multiplexed with the EEDO and

RXFRTGD pins.

Power Good

Input

The PG pin has two functions: (1) it puts the device into

Magic Packet mode, and (2) it blocks any resets when

the PCI bus power is off.

When PG is LOW and either MPPEN or MPMODE is

set to 1, the device enters the Magic Packet mode.

When PG is LOW, a LOW assertion of the PCI RST pin

will only cause the PCI interface pins (except for PME)

to be put in the high impedance state. The internal logic

will ignore the assertion of RST.

When PG is HIGH, assertion of the PCI RST pin

causes the controller logic to be reset and the configu-

ration information to be loaded from the EEPROM.

RWU

Remote Wake Up

Output

RWU is an output that is asserted either when the con-

troller is in the Magic Packet mode and a Magic Packet

frame has been detected, or the controller is in the Link

Change Detect mode and a Link Change has been de-

tected.

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