Eurotech Appliances VIPER / VIPER-LITE PXA255 - Manual (Page 60)

VIPER Technical Manual Detailed hardware description
© 2007 Eurotech Ltd Issue E 60
USB host interface
There are two USB interfaces on the VIPER. These comply with the Universal Serial
Bus Specification Rev. 1.0a, supporting data transfer at full-speed (12 Mbit/s) and low-
speed (1.5 Mbit/s).
There are four signal lines associated with each USB channel:
• VBUS
• DPOS
• DNEG
• GND
Their arrangement is summarized in the following illustration:
A USB power control switch controls the power and protects against short-circuit
conditions. See the section
361H
USB power management , page
362H
83 , for details of control.
If the USB voltage is short-circuited, or more than 500mA is drawn from either supply,
the switch turns off the power supply and automatically protects the device and board.
The VBUS power supply is derived from the VIPER +5V supply.
If you require details for the USB bus, or would like to determine whether particular
peripherals are available, see
58H
www.usb.org .
1
2
3
4
1
2
3
4
1 2
10 (SHIELD) (SHIELD) 9
VBUS 1
DNEG 1
DPOS 1
GND
VBUS 2
DNEG 2
DPOS 2
GND
USB Type A Plug 1 USB Type A Plug 2 PL7
VL