SECTION 4
Power Management
4-2 PEN*KEY
R
6100 Computer Programmer’s Reference Guide
The layer immediately above the APM BIOS includes the operating system
power management driver. For DOSĆbased systems, the device driver is
NORDOSPM.EXE. For Windows applications, the device driver is
NORWINPM.DRV, and VPOWERD.386 is included. The operating system driver
is responsible for the power management strategy. This includes system power
state and device power state transitions. The driver is also responsible for the
application interfaces.
The highest layer includes applications that are
APMĆaware
. Applications reĆ
ceive power messages only from the APM driver. Applications can communicate
with either the APM driver or the APM BIOS.
The objective of APM is to control the power usage of the system according to
system activity. As system activity decreases, APM reduces the power consumpĆ
tion of system resources until the system is brought into a suspend state.
There are two methods of powerĆlevel control:
"
The APM BIOS manages CPU/core logic, display, and backlight power in
the background, based on device activity.
"
An APM driver (NORDOSPM.EXE or NORWINPM.DRV and
VPOWERD.386) participates in managing power levels via function calls to
the APM software interface.
System Power States
The APM driver has three default system power states:
"
Ready ( full on )
"
Idle
"
APM suspend.
The primary difference between states is the latency needed for the system to
reach full operation. Power consumption and performance are greatest in the
Ready state and decrease with each succeeding state.
"
System Ready is the default mode when the system is not engaged in power
management.
"
System Idle is the first level of power management. The CPU is halted and
the system clock speed is reduced. Transitions from Idle to Ready are
instantaneous.
"
System Suspend is the second level of power management. The CPU clock
is stopped and devices are placed into the power state defined by the apĆ
plication for System Suspend. The device power state for suspend can be
any power state defined for that device. The exact definition of a device
power state during suspend is performed by using the
Set Power State, Get
Power State,
and
Enable/Disable Device Power Management
functions.
Transitions from suspend to ready generally take 100 milliseconds.
System Power State Management
System power states are managed through the use of activity monitors, activity
timers, and function calls from APM device drivers or APMĆaware applications.
Activity monitors are hardwareĆspecific devices that watch for I/O to predefined
I/O devices and I/O addresses. The PEN*KEY 6100 system has activity moniĆ
tors for the following I/O devices. Whenever one of these devices is accessed, a
bit in the activity monitor for the device becomes set.
4. Power Management
Содержание PEN*KEY 6100
Страница 1: ...PEN KEYR 6100 Computer PROGRAMMER S REFERENCE GUIDE P N 977 054 001 Revision B December 2000 ...
Страница 14: ...CONTENTS xii PEN KEYR 6100 Computer Programmer s Reference Guide ...
Страница 22: ...Preface 8 PEN KEYR 6100 Computer Programmer s Reference Guide PREFACE ...
Страница 112: ...SECTION 4 Power Management 4 10 PEN KEYR 6100 Computer Programmer s Reference Guide 4 Power Management ...
Страница 318: ...GENERAL INDEX Index 6 PEN KEYR 6100 Computer Programmer s Reference Guide ...