UM0842 datasheet(29/50 Pages) STMICROELECTRONICS

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UM0842

CPU board hardware description

Doc ID 16542 Rev 4

29/50

A.2

Block descriptions

A.2.1

Dynamic memory subsystem

The Dynamic memory subsystem is composed of three major parts:

Memory chip

The SPEAr320 MPU supports up to 256 Mbytes of memory. Place and route is provided for

2 chips but only one has been populated. The memory used is a Micron DDR2 device, its

part number is MT47H64M16HR-3 and its size is 128 Mbits x 8 (16 Mbits x 8 x 8 banks).

Local power supply

The local power supply is based on a monolithic voltage regulator for the chip set and

DDR2/3 (PM6641). It is generated locally in order to minimize the layout impact and also to

avoid any noise injection between different subsystems.

Signal termination

A parallel termination is added on the clock lines to compensate, if needed, for 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 SPEAr320

MPU and the memory sides).

A.2.2

Static memory subsystem

Serial Flash memory

The SPEAr320 MPU supports up to 16 Mbytes of Serial Flash memory. Place and route for

2 blocks of 8 Mbytes are provided on the board but only one is populated. It is based on an

M25P64-VMF6P (Numonix) Serial Flash memory device.

A resistor (R8) is also provided to protect the Flash memory from any unwanted write

access.

A.2.3

USB 2.0 subsystem

Host ports

The board has two host ports that are fully compliant with the USB 2.0 specification (two

controllers with one port each). This means that the two hosts can work in concurrent mode

with the maximum possible bandwidth. Each host has also full control of the VBUS supplied

by the ST2052 power switch that also provides overcurrent protection in case of a short

circuit in the USB cable.

Device port

A USB 2.0 device port is also provided.

A.2.4

Debug interface

The JTAG interface can be used for "static" debugging. This means that it is possible to set a

breakpoint and, when the system stops, verify the contents of the memory and/or registers

and modify them if needed.

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