User Guide

Nokia Customer Care System Module

Company Confidential RH-21

Issue 2 07/2004  2004 Nokia Corporation. Page 15

Accessories Interface

System connector

Introduction

RH-21 uses DCT4-accessories via DCT4 system connector.

Interface

The interface is supported by DCT4-compatible, fully differential 4-wire (XMICN, XMICP,

XEARN, and XEARP) accessories.

Figure 5: System Connector.

An accessory is detected by the HeadInt- line, which is connected to the XMIC. When

accessory is connected, it generates headint- interruption (UEMINT) to MCU. After that,

hookInt line is used to determine which accessory is connected. This is done by the volt-

age divider, which consists of phone's internal pull-up and accessory specific pull-down.

Voltage generated by this divider is then read by the ad- converter of UEM. The HookInt-

interrupt is generated by the button in the headset or by the accessory external audio

input.

VIN

XMICP

MICN MIC

GND

XMICN

HEADI HFC

PWMO