MEC1632 datasheet(172/636 Pages) MICROCHIP

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MEC1632

DS00001592B-page 172

 2012-2018 Microchip Technology Inc.

9.7

Low Power Modes

The ACPI Embedded Controller Interface (ACPI-ECI) automatically enters low power mode when no transaction targets

it.

9.8

Description

The ACPI Embedded Controller Interface (ACPI-ECI) provides an APCI-EC interface that adheres to the ACPI specifi-

cation. The ACPI Embedded Controller Interface (ACPI-ECI) includes two modes of operation: Legacy Mode and Four-

byte Mode.

The ACPI Embedded Controller Interface (ACPI-ECI) defaults to Legacy Mode which provides single byte Full Duplex

operation. Legacy Mode corresponds to the ACPI specification functionality as illustrated in FIGURE 9-2: on page 173.

The EC interrupts in FIGURE 9-2: on page 173 are implemented as EC_OBF & EC_IBF. See Section 9.6, "Interrupts,"

on page 171.

In Four-byte Mode, the ACPI Embedded Controller Interface (ACPI-ECI) provides four byte Full Duplex operation. Four-

byte Mode is a superset of the ACPI specification functionality as illustrated in FIGURE 9-2: on page 173.

Both Legacy Mode & Four-byte Mode provide Full Duplex Communication which allows data/command transfers in one

direction while maintaining data from the other direction; communications can flow both ways simultaneously.

In Legacy Mode, the ACPI Embedded Controller Interface (ACPI-ECI) contains three registers: ACPI OS COMMAND

in the ACPI_OS address space (see Table 9-9).

The OS2EC Data EC-Register Byte 0 and ACPI OS COMMAND Register registers appear as a single 8-bit data register

in the ACPI_EC address space. The CMD bit in the STATUS OS-Register is used by the ACPI_EC to discriminate com-

mands from data written by the ACPI_OS to the ACPI_EC. The CMD bit is controlled by hardware: ACPI_OS writes to

the OS2EC Data EC-Register Byte 0 register clear the CMD bit; ACPI_OS writes to the ACPI OS COMMAND Register

set the CMD bit.

MEC1632 Datasheet(PDF) 172 Page - Microchip Technology