Motorola Commercial CM Series Service-informatie - Pagina 7
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1.0
Introduction
This Chapter provides a detailed theory of operation for the Controlhead circuits. For details of the
trouble shooting refer to the related chapter in this section.
2.0
Controlhead Model for CM140 and CM340
The controlhead 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
DTMF
DTMF
Resistors
Resistors
Keypads
Keypads
2.1
Power Supplies
The power supply to the control 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 control 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