User Guide

6255/6255i6256/6256i (RM-19)

Baseband Description and Troubleshooting Nokia Customer Care

Figure 20: FM Radio signals after Radio on

USB Interface

The USB (Universal Serial Bus) allows up to 127 devices to be attached via a tree-like

structure of hubs and devices all emanating from one root host. Devices can be attached

or detached at any time without concern for rebooting the PC or loading device driver

software. Detection of attachment or detachment is done automatically and requires no

user input.

The mobile terminal is a full speed peripheral device, and as such, communicates with

the host PC at 12Mbps. Full speed USB allows for fast transfer of large data formats

(MP3, JPEG, AVI, etc.). When the mobile terminal is used as a modem, a fast interconnect

with the PC is required.

The mobile terminal incorporates the portal USB engine. This engine is supported using

an ASIC core supplied by TI. This core is called the Wireless Function Controller 2 (W2FC)

and is included in the D2800 processor IC. The core completes several USB functions

automatically and is controlled by the ARM9 MCU.

Because the D2800 processor's IO cells are restricted to 1.8V, the Nokia USB Transceiver

(NUT) is used as a data-level, shifting and conditioning ASIC. NUT provides the interface

between the ASIC's 1.8V bus and the 3.3V USB bus. Before the USB signals are passed to

the system connector, they pass through an Application Specific Integrated Passive

(ASIP) that integrates five passive components and provides >8kV ESD protection for the

external data and power supply lines.