Eurotech Appliances ZEUS PXA270 - Manual (Page 71)

ZEUS Technical Manual Power and power management
© 2007 Eurotech Ltd Issue D 71
Ethernet power management
The Ethernet controllers (Davicom DM9000A) incorporate a number of features to
maintain the lowest power consumption.
The device can be put into a power-reduced mode by setting the PHY control register
bit 16.4. In power-reduced mode, the device transmits the fast link pulses with
minimum power consumption. It also monitors the media for the presence of a valid
signal and, if detected, the device automatically wakes up and resumes normal
operation. The power consumption in power-reduced mode (without the cable) is
31mA.
The PHY can be put into a sleep mode by setting the PHY control register bit 16.1,
which powers down all the circuits except the oscillator and clock generator circuit.
The PHY can be put into a power-down mode by setting the PHY control register bit
0.11, which disables all transmit and receive functions but not access to PHY registers.
The power consumption in power-down mode is 63mW. The system clock can be
turned off, by using the SCCR register (bit 0) of DM9000A, to further reduce the power
consumption to 22mW.
For more information about power management, refer to the DM9000A datasheet on
the Development Kit CD.
Audio power management
The audio CODEC (Wolfson WM9712L) supports the standard power down control
register defined by AC’97 standard (26h). In addition, the individual sections of the chip
can be powered down through register 24h. Significant power savings can be achieved
by disabling parts of WM9712L that are not used.
Shutting down all the clocks and digital and analogue sections can reduce WM9712L
consumption down to near zero (1.65μW).
For more information about power management, refer to the WM9712L datasheet on
the Development Kit CD.
LVDS power management
If not used, the DS90C363 LVDS transmitter can be placed in power down mode by
applying a low-level to GPIO21 of PXA270 (signal LVDS_EN). The power consumption
in power down mode is 180μW.
CPU_ GPIO21 (LVDS_EN) LVDS operation status
0 Power down mode
1 Normal operation