Motorola Gm328 Gm338 Gm398 Detailed 6804112j18 E Manual

GM398 Model (GCN6115_)1-3
3.0 GM398 Model (GCN6115_)
The Controlhead contains the On/Off/Volume knob, the microphone connector, several buttons to 
operate the radio, several indicator Light Emitting Diodes (LED) to inform the user about the radio 
status, and a Liquid Crystal Display (LCD) with 21 pre - defined symbols and a 32*96 dot matrix for 
graphical or alpha - numerical information e.g. channel number, select code, call address name. To 
control the LEDs and the LCD, and to communicate with the...

1-4GM398 Model (GCN6115_)
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2-1
Section 2
THEORY OF OPERATION
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 Section of this manual.
2.0 Controlhead Model for GM328
The controlhead contains the internal speaker, the On/Off/Volume knob, the microphone connector, 
several buttons to operate the radio and several indicator Light Emitting Diodes (LED) to inform the 
user about the radio status. To control the LED’s and to...

2-2Controlhead Model for GM328
2.3 Microprocessor Circuit
The controlhead uses the Motorola 68HC11E9 microprocessor (µP) (U0831) to control the LED’s 
and to communicate with the host radio. RAM and ROM are contained within the microprocessor 
itself.
The microprocessor generates it’s clock using the oscillator inside the microprocessor along with a 8 
MHz ceramic resonator (U0833) and R0920.
The microprocessor’s RAM is always powered to maintain parameters such as the last operating 
mode. This is...

Controlhead Model for GM3282-3
2.5 Keypad Keys
The controlhead keypad is a 6-key keypad. All keys are configured as 2 analogue lines read by µP  
pins 13 and 15 . The voltage on the analogue lines varies between 0 volts and +5 volts depending on 
which key has been pressed. If no key is pressed, the voltage at both lines will be 5 volts. The key 
configuration can be thought of as a matrix, where the two lines represent one row and one column. 
Each line is connected to a resistive divider powered by +5...

2-4Controlhead Model for GM338
The HOOK input (J0811-3) is used to inform the µP  when the microphone´s hang-up switch is 
engaged. Dependent on the CPS programming the µP  may take actions like turning the audio PA on 
or off. While the hang up switch is open, line HOOK is pulled to +5 volts level by R0841. Transistor 
Q0841 is switched on and causes a low at µP  port PA1. When the HOOK switch is closed, signal 
HOOK is pulled to ground level. This switches off R0841and the resulting high level at µP...

Controlhead Model for GM3382-5
controlhead’s microprocessor wants to send data via SBEP bus. When the radio returns a data 
request message, the microprocessor will inform the radio about the pressed knob. If the radio was 
switched off, the radio’s µP  will switch it on and vice versa. If the On/Off/Volume knob is pressed 
while the radio is on, the software detects a low state on line ON OFF SENSE, the radio is alerted 
via line ON OFF CONTROL and sends a data request message. The controlhead µP  will...

2-6Controlhead Model for GM338
When the controlhead µP  wants to communicate to the host radio, the µP  brings request line CH 
REQUEST to a logic “0” via µP  pin 62. This switches on Q0823, which pulls line ON OFF 
CONTROL high through diode D0821. A low to high transition on this line informs the radio, that the 
controlhead requires service. The host radio then sends a data request message via BUS+ and the 
controlhead µP  replies with the data it wanted to send. This data can be information like...

Controlhead Model for GM3382-7
3.7 Liquid Crystal Display (LCD)
The LCD H0971 uses the display driver U0971. The display is a single layer super twist nematic 
(STN) LCD display. It has 14 characters with a 5*8 dot matrix for displaying alpha - numerical 
information and a line with 21 pre - defined icons above the dot matrix
The driver contains a data interface to the µP, an LCD segment driver, an LCD power circuit, an 
oscillator, data RAM and control logic. At power up the driver’s control logic is...

2-8Controlhead Model for GM338
Line PTT IRDEC (J0811-6) is used to key up the radio’s transmitter. While the PTT button on a 
connected microphone is released, line PTT IRDEC is pulled to +5 volts level by R0843. Transistor 
Q0843 is switched on and causes a low at µP port PA2. When the PTT button is pressed, signal 
PTT IRDEC is pulled to ground level. This switches off Q0843 and the resulting high level at µP port 
PA2 informs the µP about the pressed PTT button. The µP will inform the host radio about...