VIPER
Detailed hardware description
Memory
The VIPER has four types of memory fitted:
1MByte of bootloader FLASH containing Redboot to boot embedded Linux or
VxWorks, or Eboot to boot Windows CE .NET.
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A resident FLASH disk containing the OS and application images.
SDRAM for system memory.
256KBytes of Static RAM (SRAM).
Bootloader FLASH
A 1MByte Bottom Boot FLASH EPROM device, arranged as 512Kbit x 16, is used as
the bootloader FLASH. It holds Redboot (for embedded Linux or VxWorks) or Eboot (for
Windows CE .NET), together with configuration information. When the microprocessor
comes out of reset it boots the relevant bootloader from here, which in turn boots up the
OS from the FLASH memory/silicon disk. Whenever the Bootloader FLASH memory is
accessed the FLASH access LED illuminates.
FLASH memory/silicon disk
The VIPER supports 16MBytes or 32MBytes of Intel StrataFLASH memory for the OS
and application images. The FLASH memory is arranged as 64Mbit x 16-bits (16MByte
device) or as 128Mbit x 16-bits (32MByte device) respectively.
The FLASH memory array is divided into equally sized symmetrical blocks that are
64-Kword in size. A 128Mbit device contains 128 blocks, and 256Mbit device contains
256 blocks. Flash cells within a block are organized by rows and columns. A block
contains 512 rows by 128 words. The words on a row are divided into 16 eight-word
groups.
The PXA255 GPIO14 pin is connected to the FLASH memory status output. This pin
can be used to generate an interrupt to indicate the completion of a CFI command.
Whenever the FLASH memory is accessed the FLASH access LED illuminates.
SDRAM interface
There are two memory configurations supported by the VIPER: 16MBytes or 64MBytes
of SDRAM located in Bank 0. The SDRAM is configured as 4MBytes x 32-bits
(16MBytes) or 16MBytes x 32-bits (64MBytes), by 2 devices with 4 internal banks of
1MBytes or 4MBytes x 16-bits.
These are surface mount devices soldered to the board and cannot be upgraded.
RedBoot (embedded Linux and VxWorks) automatically detects the amount of memory
fitted to the board, and configures the SDRAM controller accordingly. For Windows CE
.NET applications the SDRAM memory will always be 64MBytes.
The SDRAM controller supports running the memory at frequencies between 50MHz
and 99.5MHz (default). This can be configured to achieve the optimum balance
between power consumption and performance.
© 2004 Arcom Issue H
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