Eurotech VIPER, Technical Manual, Page: 74 / 111

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:
•
383H
Processor current estimations , page
384H
75 .
•
385H
Power savings , page
386H
77 .
•
387H
External peripheral device power estimations , page
388H
78 .
•
389H
Power estimate examples , page
390H
79 .
The sections immediately following these detail the VIPER features that can be
shutdown. See pages
391H
81 to
392H
84 .
The section
393H
Processor current estimations , page
394H
75 , 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).
The section
395H
Power savings , page
396H
77 , 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.
The section
397H
External peripheral device power estimations , page
398H
78 , provides some
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.
The section
399H
Power estimate examples , page
400H
79 , provides some examples to help you
better understand how to use the information provided within the tables of the
401H
Processor current estimations ,
402H
Power savings and
403H
External peripheral device power
estimations sections.