VIPER
Power and power management
USB power management
The USB Host controller supports a USB suspend state. Placing the controller into the
USB suspend state can reduce the power consumption of the VIPER by up to 21mA
(105mW). To suspend the USB, the software must write to the relevant bits in the
HcControl Register (81h). Please see the ISP1160 datasheet contained on the
Development Kit CD.
Audio power management
The audio interface supports the AC’97 low power modes. Shutting down the digital and
analog interfaces can reduce consumption by up to 54mA (270mW).
To shut down the AC’97 Codec, the software must write to the relevant bits in the
Powerdown Control / Status Register (26h). Please see the LM4548A datasheet
contained on the Development Kit CD.
Wake up events
When the PXA255 processor is placed into sleep mode, a number of different sources
can be used to wake the processor. Below is a list of sources, and the related PXA255
GPIO signal.
Source GPIO
Ethernet GPIO0
PC/104 IRQ
GPIO1
USB GPIO2
COM5 GPIO3
COM4 GPIO4
RTC Alarm
Internal
See section 3.5 in the PXA255 Applications Processor Developers Manual, included in
the Development Kit CD.
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