UM0805

Block descriptions

Doc ID 16304 Rev 3

9/29

6

Block descriptions

6.1

Dynamic memory subsystem

The Dynamic memory subsystem is composed of three major parts:

6.1.1

Memory chip

The memory used is a Micron DDR2 device and its part number is: MT47H64M16HR-3. Its

size is 128 Mb x 8 (16 Mb x 8 x 8 banks).

6.1.2

Local power supply

It is based on a linear regulator with a low drop voltage (LD1117-1.8). It is generated locally

in order to minimize the layout impact and also to avoid any noise injection between different

subsystems.

6.1.3

Signal termination

A parallel termination is added on the clock lines to compensate, if needed, the layout

dissymmetry. Two 100 Ohm resistors are used for each line in order to obtain an impedance

of 50 ohms. All the other terminations are directly inside the pads (both on the SPEAr600

and the memory sides).

6.2

Static memory subsystem

6.2.1

Serial Flash memory

This block is based on an M25P64 ST Serial Flash memory device. The size of this chip is 8

MB and with both the two banks populated we have a total of 16 Mbytes.

A switch (SW2-2) is also provided to protect the Flash memory from any unwanted write

access.

6.2.2

It also has a switch (SW2-3) to protect the EEPROM from unwanted write access.

6.2.3

NAND Flash memory

This block is based on ST NAND Flash NAND512W3A (U12) its size is 64 MB and its bus

width x8. If required this chip can be replaced and another can be used. To do this, deselect

the on-board Flash by removing jumper JP5 and connect an adapter board on J21.

Figure 4.

NAND Flash memory selection

1

2

3

JP 5

U12

D e-selected

1

2

3

JP 5

U12

Selected