Inside Macintosh: Devices /

Chapter 6 - Power Manager

This chapter describes the Power Manager, the part of the Macintosh Operating System that controls power to the internal hardware devices of battery-powered Macintosh computers (such as the Macintosh Portable, the Macintosh PowerBook computers, and the Macintosh Duo computers)

The Power Manager automatically shuts off power to internal devices to conserve power whenever the computer has not been used for a predetermined amount of time. In addition, the Power Manager allows your application or other software to

• install a procedure that is executed when power to internal devices is about to be shut off or when power has just been restored
• set a timer to wake up the computer at some time in the future
• set or disable the wakeup timer and read its current setting
• enable, disable, or delay the CPU idle feature
• read the current CPU clock speed
• control power to the internal modem and serial ports
• read the status of the internal modem
• read the state of the battery charge and the status of the battery charger

Most applications do not need to know whether they are executing on a battery-powered Macintosh computer because the transition between power states is largely invisible. As a result, most applications do not need to use Power Manager routines. You need the information in this chapter only if you are writing a program--such as a device driver--that must control power to some subsystem of a battery-powered Macintosh computer or that might be affected by the idle or sleep state. See "About the Power Manager," beginning on page 6-4, for a complete description of these power conservation states.

The Power Manager is available only in system software version 6.0.4 and later versions. You should use the Gestalt function to determine whether the Power Manager is available before calling it. See "Determining Whether the Power Manager Is Present," on page 6-14, for more information.

To use this chapter, you might need to be familiar with techniques for accessing information in your application's A5 world. The chapter "Introduction to Memory Management" in Inside Macintosh: Memory describes the A5 world and the routines you can use to manipulate the A5 register. This chapter provides complete code samples that illustrate how to access your application's A5 world in a sleep procedure. If you wish to display a dialog box from a sleep procedure, you also need to know about the Dialog Manager. See the chapter "Dialog Manager" in Inside Macintosh: Macintosh Toolbox Essentials.

This chapter begins with a preliminary description of the power conservation states controlled by the Power Manager and of the relationship between the power management hardware and software in portable Macintosh computers. It then discusses the power conservation states and the sleep queue in greater detail. The section "Using the Power Manager," beginning on page 6-13, describes how to use Power Manager routines to control the power conservation states and how to write and install sleep procedures.

The reference section is divided into three sections. The first section describes the data structures used by Power Manager routines. The second section, "Power Manager Routines," beginning on page 6-28, describes low-level Power Manager routines that you can use to control a variety of Power Manager functions. The third section, "Power Manager Dispatch Routines," beginning on page 6-40, describes high-level Power Manager routines that isolate you from the need to read or write directly to the Power Manager's private data structures and to parameter RAM. The Power Manager dispatch routines provide access to most of the Power Manager's internal parameters. Where a Power Manager dispatch routine duplicates the function of another Power Manager routine, the dispatch routine provides the preferred interface.

Whereas the Pascal programming language interface is used to describe the Power Manager routines in "Power Manager Routines," the C language interface is used for the newer routines described in "Power Manager Dispatch Routines." The section "Summary of the Power Manager," beginning on page 6-67, includes both Pascal and C interfaces for both sets of routines.

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Chapter Contents

About the Power Manager

The Power-Saver State

The Idle State

The Sleep State

The Sleep Queue

Sleep Requests

Sleep Demands

Wakeup Demands

Sleep-Request Revocations

Power Manager Dispatch

Using the Power Manager

Determining Whether the Power Manager Is Present

Determining Whether the Power Manager Dispatch Routines are Present

Enabling or Disabling the Idle State

Setting, Disabling, and Reading the Wakeup Timer

Installing a Sleep Procedure

Using Application Global Variables in Sleep Procedures

Writing a Sleep Procedure

Switching Serial Power On and Off

Monitoring the Battery and Battery Charger

Power Manager Reference

Data Structures

Sleep Queue Record

Hard Disk Queue Structure

Wakeup Time Structure

Battery Information Structure

Battery Time Structure

Power Manager Routines

Controlling the Idle State

Controlling and Reading the Wakeup Timer

Controlling the Sleep Queue

Controlling Serial Power

Reading the Status of the Internal Modem

Reading the Status of the Battery and the Battery Charger

Power Manager Dispatch Routines

Determining the Power Manager Features Available

Controlling the Sleep and Wakeup Timers

Controlling the Dimming Timer

Controlling the Hard Disk

Getting Information About the Internal Batteries

Controlling the Internal Modem

Controlling the Processor

Getting and Setting the SCSI ID

Application-Defined Routines

Sleep Procedures

Hard Disk Spindown Function

Summary of the Power Manager

Pascal Summary

Constants

Data Types

Power Manager Routines

Power Manager Dispatch Routines

Application-Defined Routines

C Summary

Constants and Data Types

Power Manager Functions

Power Manager Dispatch Functions

Application-Defined Functions

Assembly-Language Summary

Data Structures

Trap Macros

Result Codes