
MOTOROLA
Chapter 10. Power Management
10-3
Programmable Power Modes
10.3.1 Power Management Modes
The following sections describe the characteristics of the G2 core power management
modes, the requirements for entering and exiting the various modes, and the system
capabilities provided by the G2 core while the power management modes are active.
10.3.1.1 Full-Power Mode with DPM Disabled
Full-power mode with DPM disabled is selected when the DPM enable bit in HID0[DPM]
is cleared. The following characteristics apply:
Default state following power-up and core_hreset
All functional units are operating at full processor speed at all times
10.3.1.2 Full-Power Mode with DPM Enabled
Full-power mode with DPM enabled (HID0[DPM] = 1) provides on-chip power
management without affecting the functionality or performance of the G2 core as follows:
Required functional units are operating at full processor speed
Functional units are clocked only when needed
No software or hardware intervention required after mode is set
Software/hardware and performance transparent
10.3.1.3 Doze Mode
Doze mode disables most functional units but maintains cache coherency by enabling the
bus interface unit and snooping. A snoop hit causes the G2 core to enable the data cache,
copy the data back to memory, disable the cache, and fully return to the doze mode.
Table 10-1. G2 core Programmable Power Modes
PM Mode
Functioning Units
Activation Method
Full-Power Wake-Up Method
Full power
All units active
—
—
Full power
(with DPM)
Requested logic by demand By instruction dispatch
—
Doze
Bus snooping
Data cache as needed
Decrementer timer
Controlled by SW
External asynchronous exceptions
Decrementer interrupt
Reset
Nap
Decrementer timer
Controlled by hardware and
software
External asynchronous exceptions
Decrementer interrupt
Reset
Sleep
None
Controlled by hardware and
software
External asynchronous exceptions
Reset
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