Eurotech Appliances ZEUS PXA270 - Manual (Page 33)

ZEUS Technical Manual Detailed hardware description
© 2007 Eurotech Ltd Issue D 33
Memory
The ZEUS has four types of memory fitted:
• 32 or 64MB resident Flash disk containing:
- Boot loader to boot operating system.
- Operating system.
- Application images.
• 64, 128 or 256MB of SDRAM for system memory.
• Static RAM, as follows:
- 256KB of SRAM internal to PXA270.
- 256KB of SRAM external to PXA270 (battery backed).
• 128 bytes of configuration EEPROM on the I²C bus.
Flash memory
The ZEUS supports 32MB or 64MB of Spansion (AMD) MirrorBit Flash memory for the
boot loader, OS and application images. The Flash memory is arranged as 128Mbit x
16-bit (32MB device) or as 256Mbit x 16-bit (64MB device).
The Flash memory array is divided into equally sized symmetrical blocks that are
64-Kword in size (128KB) sectors. A 256Mbit device contains 256 blocks, and a
512Mbit device contains 512 blocks.
Whenever the Flash memory is accessed the ‘Flash’ access LED is illuminated.
SDRAM
There are two standard memory configurations supported by the ZEUS: 64MB or
128MB of SDRAM located in banks 0 and 1. The SDRAM is configured as 16MB x 32-
bit (64MB), or 32MB x 32-bit (128MB). 64MB configuration is using 2 devices, and
128MB configuration is using 4 devices, each with 4 internal banks of 4MB x 16-bit.
Optional 256MB configuration is using 4 devices, each with 4 internal banks of 8MB x
16-bit.
These are surface mount devices soldered to the board. The size of memory fitted to
the board is detected by software to configure the SDRAM controller accordingly.
The SDRAM memory controller is set to run at frequency of 104MHz.