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ZEUS Technical Manual Power and power management
© 2007 Eurotech Ltd Issue D 66
Processor power management
First available in the PXA270 processor, Wireless Intel SpeedStep Technology
dynamically adjusts the power and performance of the processor based on CPU
demand. This can result in a significant decrease in power consumption.
In addition to the capabilities of Intel Dynamic Voltage Management, the Intel XScale
micro architecture of the PXA27x family incorporates three new low power states.
These are deep idle, standby and deep sleep. It is possible to change both voltage and
frequency on the fly by intelligently switching the processor into the various low power
modes. This saves additional power while still providing the necessary performance to
run rich applications.
Wireless Intel SpeedStep technology includes the following features:
• Five reset sources: power-on, hardware, watchdog, GPIO and exit from sleep and
deep-sleep modes (sleep-exit).
• Multiple clock-speed controls to adjust frequency, including frequency change,
turbo mode, half-turbo mode, fast-bus mode, memory clock, 13M mode, A-bit mode
and AC ’97.
• Switchable clock source.
• Functional-unit clock gating.
• Programmable frequency-change capability.
• One normal-operation power mode (run mode) and five low power modes to control
power consumption (idle, deep-idle, standby, sleep and deep-sleep modes).
• Programmable I
2
C-based external regulator interface to support changing dynamic
core voltage, frequency change and power mode coupling.
The PXA270 power consumption depends on the operating voltage and frequency,
peripherals enabled, external switching activity, external loading and other factors. The
tables below contain power consumption information at room temperature for several
operating modes: active, idle and low power. For active power consumption data, no
PXA270 peripherals are enabled except for on-chip UARTs.