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ZEUS Technical Manual Power and power management
© 2007 Eurotech Ltd Issue D 70
CompactFlash power management
The power supply to the CompactFlash interface is controlled via software, and
supports hot swap card insertion and CompactFlash power down states. GPIO97 on
the PXA270 (signal CF_PWEN) is used to control the power supply switch. Setting this
line to logic ‘0’ switches off the power to the CompactFlash interface. The current-
limiting (1A) and thermal protection features of the power switch eliminate the need for
the fuse. The power supply to the CompactFlash is derived from 3.3V supply.
CPU_ GPIO97 (CF_PWEN) CF power
0 Power off
1 Power on
Wireless modem power management
The power supply to the wireless modem interface (VCC_MODEM) is controlled by
SYS_EN signal of the PXA270, and is switched off when PXA270 is in deep-sleep
mode. The current-limiting (2A) and thermal protection features of the power switch
eliminate the need for the fuse. VCC_MODEM power supply is derived from the ZEUS
+5V supply.
GSM_ON and GPS_ON control signals are provided on the ZEUS Modem connector
(J23). They are controlled by on-board GPIO expander (see On-Board GPIO
expanders pin assignments
, page 29). For details on how to use these signals, and
other power management features of the specific wireless and GPS devices, please
consult the datasheet of the device used.
USB power management
A USB power control switch controls the power, and protects against short-circuit and
over-current conditions, on USB host ports.
If the USB voltage VBUSx is short-circuited, or more than 500mA is drawn from any
VBUSx supply, the switch turns off the power supply and protects the device and board
automatically. The VBUSx power supplies are derived from the ZEUS +5V supply.
The following table shows the PXA270 assignments for power enable and over-current
signals:
Host 1/2 functions PXA270 GPIO Active
USB_PWE1 GPIO89 High
USB_OC1# GPIO88 Low
USB_PWE2 GPIO22 High
USB_OC2# GPIO114 Low