2192-12132-000-000
Power Supply
The VIPER is designed to operate from a 5V ± 5% (4.75V to +5.25V) supply. The power
connector PL12 has a +12V connection defined, but is not required for the VIPER under normal
operation. It can be used to 12V to the PC/104 stack if required.
The power connector PL14 is part number:
Molex 22-05-7048
The mating connector is part number:
Molex 22-01-2045
Three other supply voltages are present on the board, these are 0.8 – 1.4V, 1.8V and +3.3V.
These supplies are required for the CPU core and on-board devices. The +3.3V supply is routed
to the CompactFlash interface, and can be used to power +3.3V flat panels via PL3.
The +5V supply is monitored automatically on-board and if this supply falls below 4.63V the
board will be placed in RESET. When the power supply rises above this threshold voltage the
board will start to operate again. This power supply monitor will ensure that the board does not
hang if the supply voltage fails at any point.
Power Management
The VIPER board supports various power management functions.
Processor
The power manager in the PXA255 offers the ability to disable the clocks to the different internal
peripherals. By default after reset all clocks are enabled. To reduce power consumption disable
the clocks for any unused peripherals. Also the clock speed of the processor core, PXbus (the
internal bus connecting the CPU core and the other blocks of the PXA255), LCD and SDRAM
can be changed to achieve a balance between performance and power consumption. For more
details on the internal power manager please refer to the PXA255 documentation on a
Development Kit CD.
UARTS
COM4 and COM5 are generated from an external 16C2852 DUART. This device supports a
sleep mode with an auto wake up. By enabling this feature the DUART will enter sleep mode
when there are no interrupts pending. The part will resume normal operation when any of the
following occurs: receive data start bit, change of state on: CTS, DSR, CD, RI or data is being
loaded into transmit FIFO. If the part was awakened by one of the above conditions, it will return
to the sleep mode automatically after the condition has cleared. Please refer to the 16C2852
datasheet on a Development Kit CD, or information on enabling the sleep mode.
GP12 and GP13 on the PXA255 can be used to power down the RS232 drivers on the VIPER,
to save power. The table shows the affect of GP12 and GP13 on the RS232 drivers, placing the
drivers in shutdown mode offers the greatest power saving.
GP12 GP13 Operation Status
Transmitters
Receivers
0 0
Normal
Operation Active Active
0 1
Normal
Operation Active High-Z
1 0 Shutdown
High-Z High-Z
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