Power Management Modes; Full-Power Mode With Dpm Disabled; Full-Power Mode With Dpm Enabled - Motorola MPC750 User Manual

Table 10-1. MPC750 Microprocessor Programmable Power Modes
PM Mode Functioning Units Activation Method Full·PowerWake Up Method
Full power All units active
-
-
Full power
Requested logic by By instruction dispatch
-
(with DPM) demand
Doze
• Bus snooping Controlled by SW External asynchronous exceptions'
• Data cache as needed
Decrementer interrupt
• Decrementer timer Performance monitor interrupt
Thermal management interrupt
Reset
Nap
• Bus snooping Controlled by hardware External asynchronous exceptions
- enabled by deassertion and software Decrementer interrupt
ofQACK Performance monitor interrupt
• Decrementer timer
Thermal management interrupt
Reset
Sleep None Controlled by hardware External asynchronous exceptions
and software Performance monitor interrupt
Thermal management interrupt
Reset
Note: • Exceptions are referred to as interrupts in the architecture specification.
10.2.1 Power Management Modes
The following sections describe the characteristics of the MPC750's power management
modes, the requirements for entering and exiting the various modes, and the system
capabilities provided by the MPC750 while the power management modes are active.
10.2.1.1 Full-Power Mode with DPM Disabled
Full-power mode with DPM disabled is selected when the DPM enable bit (bit 11) in HIDO
is cleared.
• Default state following power-up and HRESET
• All functional units are operating at full processor speed at all times.
10.2.1.2 Full-Power Mode with DPM Enabled
Full-power mode with DPM enabled (HIDO[DPM]
=
1) provides on-chip power
management without affecting the functionality or performance of the MPC750.
• Required functional units are operating at full processor speed.
• Functional units are clocked only when needed.
• No software or hardware intervention is required after mode is set.
• Softwarelhardware and performance transparent
10-2 MPC750 RISC Microprocessor User's Manual