Method for an external SMC to put an I/O controller hub in a sleep mode and wake it up later using an enhanced SMBUS implementation

Method for an external SMC to put an I/O controller hub in a sleep mode and wake it up later using an enhanced SMBUS implementation

Disclosed is a method for an external system management controller (SMC) to put an I/O controller hub (ICH) in a sleep mode and wake it up later using an enhanced system management bus (SMBus) implementation. Benefits include improved functionality.

Background

        � � � � � Conventional implementations of ICH devices do not provide a mechanism to put the ICH in a sleep state through the SMBus by an external system management controller.

        � � � � � The conventional format of the SMBus write command is 20 bits long (see Figure 1).

Description

        � � � � � The disclosed method enables an external system management controller (SMC) to put an I/O controller hub (ICH) in a sleep mode and wake it up later using an enhanced system management bus (SMBus) implementation (see Figure 2). The method adds a write command type, 21h, and changes the use of type 20h for toggling the pwrbtnB signal (see Figure 3).

        � � � � � When the external SMC issues command type 20h, the SMBus Logic drives the pwrbtnB bit active. When the 20h command is followed by a type 21h command, the SMC drives the pwrbtnB bit to inactive. The sending module ID (SMI#) or serial communications interface (SCI) sends a system request to transition to a sleep state. If the system is already in a sleep state, issuing command type 20 followed by command type 21 causes a wake event. In conventional impl...