AM79C975VCW datasheet(103/304 Pages) AMD

103 / 304 page

Am79C973/Am79C975

103

P R E L I M INARY

Figure 49. OnNow Functional Diagram

OnNow Wake-Up Sequence

The system software enables the PME pin by setting

the PME_EN bit in the PMCSR register (PCI configura-

tion registers, offset 44h, bit 8) to 1. When a Wake-up

event is detected, the Am79C973/Am79C975 control-

ler sets the PME_STATUS bit in the PMCSR register

(PCI configuration registers, offset 44h, bit 15). Setting

this bit causes the PME signal to be asserted. Asser-

tion of the PME signal causes external hardware to

wake up the CPU. The system software then reads the

PMCSR register of every PCI device in the system to

determine which device asserted the PME signal.

When the software determines that the signal came

from the Am79C973/Am79C975 controller, it writes to

the device’s PMCSR to put the device into power state

D0. The software then writes a 0 to the PME_STATUS

bit to clear the bit and turn off the PME signal, and it

calls the device’s software driver to tell it that the device

is now in state D0. The system software can clear the

PME_STATUS bit either before, after, or at the same

time that it puts the device back into the D0 state.

Link Change Detect

Link change detect is one of Wake-up events defined

by the OnNow specification and is supported by the

RWU mode. Link Change Detect mode is set when the

LCMODE bit (CSR116, bit 8) is set either by software

or loaded through the EEPROM.

When this bit is set, any change in the Link status will

cause the LCDET bit (CSR116, bit 9) to be set. When

MPDETECT

MPPEN

MPMODE

MPEN

MPINT

LED

WUMI

Magic Packet

Link Change

LCMODE

Link Change

MPMAT

LCDET

DET

CLR

BCR47

BCR46

BCR45

SET

CLR

SET

CLR

SET

CLR

PMAT

Pattern Match

Input

Pattern

PME_STATUS

Pattern Match RAM (PMR)

PME Status

PME_EN

MPMAT

PME_EN_OVR

LCEVENT

PME

RWU

SET

CLR

POR

H_RESET

POR

21510D-54

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