Power management – Eurotech Appliances VIPER / VIPER-LITE PXA255 User Manual
Page 74
VIPER Technical Manual
Power and power management
© 2007 Eurotech Ltd Issue E
74
Power management
All VIPER power-down features and alteration of PXA255 operating frequency are fully
supported under Embedded Linux and VxWorks. Windows CE currently provides no
power management support.
To simplify the power consumption estimation of the VIPER, the following sections
break down the process as follows:
•
, page
•
•
External peripheral device power estimations
, page
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•
The sections immediately following these detail the VIPER features that can be
shutdown. See pages
, page
, details current consumption of the
VIPER for performance and power saving modes at different clock frequencies.
Embedded Linux, Windows CE and VxWorks set up the PXA255 slightly differently:
•
Embedded Linux and VxWorks are booted from Redboot, which sets up the
PXA255 clock frequency to 100MHz (CCCR=0x121).
•
Embedded Linux changes the Redboot setting to 400MHz in performance mode
(CCCR=0x161).
•
VxWorks makes no changes to the Redboot setting.
•
Windows CE sets up the PXA255 clock frequency to 400MHz in power saving
mode (CCCR=0x241).
, only apples to Linux and VxWorks power
estimation calculations, as Windows CE currently does not provide any power
management support. This section shows potential power savings for that can be
achieved by shutting down sections of the VIPER that are not required.
External peripheral device power estimations
examples of power consumption for various supported peripherals, such as LCD
displays, CF and USB devices, which may or may not be used for your application.
, provides some examples to help you
better understand how to use the information provided within the tables of the
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