Nokia 232, 239 Service Manual sysmod

After Sales Technical Documentation

THX–4 Series Transceiver

Chapter 4

SYSTEM MODULE

Original, 09/94

THX–4

After Sales

System Module

Technical Documentation

CHAPTER 4 – SYSTEM MODULE
CONTENTS

Page No

Introduction 4–5

General 4–5
Special Features 4–5

Technical Specifications 4–5

Modes of Operation 4–5
External Signals and Connections 4–5

System Connector J1 4–6
Display Module Connector J2 4–7

Internal Signals 4–8

Connections between RF and Baseband 4–8

Functional Description 4–9

Logic Circuit Description 4–9

General 4–9
Micro–controller 4–9
Micro–controller D404 Pinout 4–9
Modem 4–11
Modem (N403) Signals 4–11
Regulators 4–11
PSL N407 Signals 4–12
Memories 4–12
EEPROM D406 Signals 4–12
Charging Control 4–13
Display Lighting 4–13

Audio Circuit Description 4–13

Transmit (TX) Signal Path 4–13
Receiver (RX) Signal Path 4–14

RF Circuit Description 4–15

Receiver Signal Path 4–15
Synthesizers 4–16
VCO’s and Buffers 4–16

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After Sales

THX–4

Technical Documentation

Transmitter 4–16
Duplexer and Spurious Rejection 4–17

System Module

List of Figures

Version 6

Figure 1: Component Layout Diagram (Top Side) – Sheet 1 4–19
Figure 2: Component Layout Diagram (Top Side) – Sheet 2 4–20
Figure 3: Component Layout Diagram (Bottom Side) – Sheet 1 4–21
Figure 4: Component Layout Diagram (Bottom Side) – Sheet 2 4–22
Figure 5: RF Circuit Diagram (A2) 4–23
Figure 6: Baseband Circuit Diagram (A2) 4–24
Figure 7: Keyboard Circuit Diagram 4–25

Version 11

Figure 8: Component Layout Diagram (Top Side) 4–26
Figure 9: Component Layout Diagram (Bottom Side) 4–27
Figure 10: RF Circuit Diagram 4–28
Figure 11: Baseband Circuit Diagram 4–29
Figure 12: Keyboard Circuit Diagram 4–30

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THX–4

After Sales

System Module

Technical Documentation

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After Sales

THX–4

Technical Documentation

Introduction

General

The system module controls the operation of the internal parts of the
phone. Its task is to control the user interface, i.e. LCD driver, keyboard,
and audio interface functions. The module performs all signalling towards
the system and carries out audio–frequency signal processing. In
addition, it controls the operation of the transceiver and stores tuning data
for the phone.

The RF unit receives and demodulates the radio frequency signal from the
base station and transmits the modulated signal to the base station.

Special Features

 Accessory connector at bottom, e.g. for RF booster and

handsfree units.

 RF connector at bottom, with RF switch for connection

to accessories.

System Module

 Extra lines to processor and ordinary lines with

additional functions to communicate with accessories.

Technical Specifications

Modes of Operation

The module has two active operating modes as follows:

 Conversation mode
 Listening mode

In the conversation mode all IC’s are active.
In the listening mode some blocks of the audio IC NANTIC are in standby

state. The transmitter and its synthesizer are switched off.

External Signals and Connections

The module has two external connectors, the system connector and the
display module connector. The system connector incorporates the
charging connector, the accessory connector and the external antenna
connector.

Amendment 10/97 Page 4–5

THX–4

After Sales

System Module

System Connector J1

Pin Name Description

1 VC Charger Input +ve
2 XEXAUD Booster power control output.
3 HOOK On hook indication for auxillary handset.
4 XEAR External earphone signal.
5 0V 0V for both charger and audio.
6 VC Charger input +ve
7 MBUS Bidirectional asynchronous data bus.
8 0V 0V for both charger and audio
9 XMIC External microphone signal
10 0V 0V for both charger and audio
11 0V For charger

Technical Documentation

12 VC Charger input +ve
13 VC Charger input +ve
14 0V 0V for charger
15 0V 0V
16 RF RF signal to duplex filter
17 RF RF signal to antenna
18 0V 0V
19 VBAT Battery voltage
20 BTEMP Battery temperature measurement, 27k pull–up

resistor to 4.8V.

21 BSI Battery size indication, 100k pull–up resistor to

+4.8V

22 0V 0V for battery

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