Chapter 2 Theory Of Operation; Introduction; Control Head Model For Cm200; Power Supplies - Motorola CM200 Service Manual

1.0

Introduction

This Chapter provides a detailed theory of operation for the Control head circuits. For details of the
trouble shooting refer to the related chapter in this section.
2.0

Control Head Model for CM200

The head contains the internal speaker, the on/off/volume knob, the microphone connector, several
buttons to operate the radio and three indicator Light Emitting Diodes (LED) to inform the user about
the radio status and a 7-segment display for numeric information.
7-segment 7-segment
display display
4
DTMF DTMF
Resistors Resistors
Keypads Keypads
2.1

Power Supplies

The power supply to the head is taken from the host radio's 9.3V via connector J803-9, The 9.3V is
used for the LEDs and back light, the 5V is used for the LCD driver and level shifter. The stabilized
3V is used for the other parts.
2.2

SPI Interface

The host radio (master) communicates with the head through its SPI bus. Three lines are
connected to the shift register (U801):SPI clock (J803-17), SPI MOSI (J803-16) and shift register
chip select (J803-15).
BCD To BCD To
7-segment 7-segment
Control line Control line
Boot_res / SCI Boot_res / SCI
Mux. Mux.
Control Control
DTMF DTMF
Row/Column Row/Column
Row/Column Row/Column 9.3V 9.3V
Keypad Keypad
Backlight Backlight
THEORY OF OPERATION
9.3V 9.3V
Shift Shift
Register Register
PTT PTT
circuit circuit
Boot_res (DTMF- Boot_res (DTMF-
Column)/ SCI Column)/ SCI
(DTMF-Row) (DTMF-Row)
Chapter 2
2 pin speaker 2 pin speaker
connector connector