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VIPER Technical Manual Detailed hardware description
© 2007 Eurotech Ltd Issue E 21
PXA255 processor
The PXA255 is a low power ARM (version 5TE) instruction set compliant RISC
processor. The PXA255 does not include a floating-point unit. The device does,
however, contain a DSP co-processor to enhance multimedia applications.
The VIPER is fitted with a 400MHz PXA255 variant and the VIPER-Lite is fitted with a
200MHz PXA255 variant. The clock source for these is a 3.6864 MHz clock, which
generates all the high-speed clocks within the device. The default run mode frequency
is 400MHz for the VIPER and 200MHz for the VIPER-Lite. Currently embedded Linux
and VxWorks supports changing the operating frequency and Windows CE will provide
support shortly. Please refer to the relevant operating system technical manual to
select an alternative operating frequency.
The processor has two supply inputs: I/O and core generated on the VIPER from the
main +5V supply input. The I/O supply is powered from +3.3V, and the core is powered
from a +1.06 to +1.3V adjustable supply. See the section
280HProcessor power
management
, page 281H81, for operation details.
The PXA255 has an integrated memory and CompactFlash controller with 100 MHz
memory bus, 32KB data and 32KB instruction caches and 2KB mini data cache for
streaming data.
The PXA255 provides up to 85 GPIO pins, many of which have been configured for
alternative functions like the AC’97 and PC card/CompactFLASH interfaces. Details of
these pin configurations are provided in the section
282HPXA255 GPIO pin assignments,
page
283H22.
The PXA255 also has the following features that can be used on the VIPER:
• Peripheral Control Module:
- 16 channel configurable DMA controller (for internal use only).
- Integrated LCD controller with unique DMA for fast colour screen support.
- Serial ports including AC’97, 3 UARTs and enhanced USB end point interface.
• System Control Module:
- General-purpose interruptible I/O ports.
- Real time clock.
- Watchdog.
- Interval timers.
- Power management controller.
- Interrupt controller.
- Reset controller.
- Two on-chip oscillators.
The PXA255 processor is packaged in a 256-pin PBGA, which is attached to the board
during the assembly process.
The PXA255 processor is a low power device and does not require a heat sink for
temperatures up to 70°C (85°C for the industrial variant).