Motorola Gm Series Detailed 6864115b62 A Manual

							Controlhead Model for GM380, and GM12802-9
prevents radio circuitry from discharging this capacitor. The +5V at the second anode of D0855 
speeds up charging of C0856, when the host radio is turned on by a high level at the ignition input 
while the supply voltage is applied to the radio. This prevents the microprocessor from accidently 
entering bootstrap mode.
4.3 Power On / Off
The On/Off/Volume knob when pressed switches the radio’s and the controlhead‘s voltage regulators 
on by connecting line ON OFF CONTROL to line UNSW 5V via D0852. Additionally, 5 volts at the 
base of digital transistor Q0853 informs the controlhead’s microprocessor about the pressed knob. 
The microprocessor asserts pin 8 and line CH REQUEST low to hold line ON OFF CONTROL at 5 
volts via Q0852 and D0852. The high line ON OFF CONTROL also informs the host radio, that the 
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 inform the 
radio about the pressed knob and the radio’s µP will switch the radio off. If the radio is switched on 
either manually or automatically it’s +5V source switches on the controlhead’s voltage regulator 
U0861 via line 5 SOURCE and transistor Q0866 and the controlhead’s microprocessor starts 
execution.
4.4 Microprocessor Circuit
The controlheadcontrolhead uses the Motorola 68HC11K4 microprocessor (uP) (U0871) to control 
the LED’s and the LCD 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 (U0873) and R0873.
The microprocessor’s RAM is always powered to maintain parameters such as the last operating 
mode. This is achieved by maintaining 5V at µP pin 76. Under normal conditions, when the radio is 
off, USW 5V is formed by FLT A+ running to D0855. C0856 allows the battery voltage to be 
disconnected for a couple of seconds without losing RAM parameters. Diode D0855 prevents radio 
circuitry from discharging this capacitor.
There are 8 analogue to digital converter ports (A/D) on the µP. They are labeled within the device 
block as PE0-PE7. These lines sense the voltage level ranging from 0 to 5V of the input line and 
convert that level to a number ranging from 0 to 255 which can be read by the software to take 
appropriate action.
Pin VRH is the high reference voltage for the A/D ports on the µP. If this voltage is lower than +5V the 
A/D readings will be incorrect. Likewise pin VRL is the low reference for the A/D ports. This line is 
normally tied to ground. If this line is not connected to ground, the A/D readings will be incorrect.
The microprocessor can determine the used keypad type by reading the level at port PE5. 
Connections S0931 – S0935 are provided by the individual keypads.
The MODB / MODA input of the µP must be at a logic „1 for it to start executing correctly. The XIRQ 
and the IRQ pins should also be at a logic „1.
4.5 SBEP Serial Interface
The host radio (master) communicates to the controlhead µP (slave) through its SBEP bus. This bus 
uses only line BUS+ for data transfer. The line is bi-directional, meaning that either the radio or the  
						

							2-10THEORY OF OPERATION
controlhead µP can drive the line. The microprocessor sends serial data via pin 79 and D0872 and it 
reads serial data via pin 78. Whenever the microprocessor detects activity on the BUS+ line, it starts 
communication.
When the host radio needs to communicate to the controlhead µP, it sends data via line BUS+. Any 
transition on this line generates an interrupt and the µP starts communication. The host radio may 
send data like display information, LED and back light status or it may request the 
controlheadcontrolhead ID or the keypad ID.
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 8. This switches on Q0852, which pulls line ON OFF CONTROL 
high through diode D0852. 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 which key has been 
pressed or that the volume knob has been rotated.
The controlhead µP monitors all messages sent via BUS+, but ignores any data communication 
between host radio and CPS or Universal Tuner.
4.6 Keypad Keys
The controlhead keypad is a 25 - key keypad. All keys are configured as 2 analogue lines read by µP 
pins 49 and 48. 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 volts. If a button is pressed, it will connect 
one specific resistor of each divider line to ground level and thereby reduce the voltages on the 
analogue lines The voltages of the lines are A/D converted inside the µP (ports PE 0 - 1) and specify 
the pressed button. To determine which key is pressed, the voltage of both lines must be considered.
An additional pair of analogue lines and A/D µP ports (PE 3 – 2) is available to support a keypad 
microphone, connected to the microphone connector J0811. Any microphone key press is 
processed the same way as a key press on the controlhead.
4.7 Status LED and Back Light Circuit
All the indicator LED’s (red, yellow, green) are driven by current sources. To change the LED status 
the host radio sends a data message via SBEP bus to the controlhead µP. The controlhead µP 
determines the LED status from the received message and switches the LED’s on or off via port PA 
6 - 4. The LED status is stored in the µP’s memory. The LED current is determined by the resistor at 
the emitter of the respective current source transistor.
The back light for keypad is controlled by the host radio the same way as the indicator LED’s using 
µP port PH 3. This port is a Pulse Width Modulator (PWM) output. The output signal charges 
capacitor C0943 through R0945. By changing the pulse width under software control, the dc voltage 
of C0943 and thereby, the brightness of the back light can be changed in 16 steps. The keypad back 
light current is drawn from the FLT A+ source and controlled by transistor Q0941. The current flowing 
through the LED’s cause a proportional voltage drop across the parallel resistors R0955, R0957. 
This voltage drop is amplified by the op-amp U0941-1. U0941-1 and Q0943 form a differential 
amplifier. The voltage difference between the base of Q0943 and the output of U0941-1 determines 
the current from the base of the LED control transistor Q0941 and in turn the brightness of the 
LED’s. The µP can control the LED’s by changing the dc level at the base of Q0943. If the base of 
Q0943 is at ground level, Q0943 is switched off and no current flows through Q0941 and the LED’s. 
If the base voltage of Q0943 rises a current flows through Q0943 and in turn through Q0941 causing 
the LED’s to turn on and a rising voltage drop across R0955, R0957. The rising voltage causes the  
						

							Controlhead Model for GM380, and GM1280 2-11
output of the op-amp to rise and to reduce the base to emitter voltage of Q0943. This decreases the 
current of Q0941 until the loop has settled.
The back light for the LCD module uses a similar circuitry. The only differences are that µP port PH2 
controls the back light brightness and that the LED’s are located on the LCD module which is 
connected via J0821. Control line BL A GREEN connects to the anodes and control line BL K 
GREEN connects to the cathodes of the LED’s.
4.8 Liquid Crystal Display (LCD)
The LCD module consists of the display and the display driver and is connected via connector 
J0821. The display is a single layer super twist nematic (STN) LCD display. It has a dot matrix of 32 * 
96 dots for displaying graphics and 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 reset by a logic „0 via 
pin 5 of J0821. The driver’s µP interface is configured to accept 8 bit parallel data input (J0821-D0-
D7) from the controlhead µP (U0871 port PC0-PC7).
To write data to the driver’s RAM the µP sets chip select (J0821-6) to logic „0 via U0871-26, RD 
(J0821-10) to logic „1 via (U0871-40) and WR (U0821-9) to logic „0 via U0871-33. With input A0 
(J0821-8) set to logic „0 via U0871-34 the µP writes control data to the driver. Control data includes 
the RAM start address for the following display data. With input A0 set to logic „1 the µP then writes 
the display data to the display RAM. When data transfer is complete the µP terminates the chip 
select and the clock activities.
The display driver’s power circuit provides the voltage supply for the display. This circuit consists of a 
voltage multiplier, voltage regulator and a voltage follower. The regulator output voltage for the 
display can be controlled electronically by a control command sent to the driver. The voltage level 
can be measured by one of the µP’s analogue to digital converters (U0871-42) via J0821-21. To 
stabilize the display brightness over a large temperature range the µP measures the temperature via 
analogue to digital converter (U0871-43) using a temperature sensor on the module (J0821-4). 
Dependent on the measured temperature the µP adjusts the driver output voltage, and in turn the 
display brightness, via parallel interface.
4.9 Microphone Connector Signals
Signals BUS+, PTT IRDEC, HOOK, MIC, HANDSET AUDIO, FLT A+, +5V and 2 A/D converter 
inputs are available at the microphone connector J0811. Signal BUS+ (J0811-7) connects to the 
SBEP bus for communication with the CPS or the Universal Tuner. Line MIC (J0811-5) feeds the 
audio from the microphone to the radio’s controller via connector J0801-4. Line HANDSET AUDIO 
(J0811-8) feeds the receiver audio from the controller (J0801-6) to a connected handset. FLT A+, 
which is at supply voltage level, and +5V are used to supply any connected accessory like a 
microphone or a handset.
The 2 A/D converter inputs (J0811-9/10) are used for a microphone with keypad. A pressed key will 
change the dc voltage on both lines. The voltages depend on which key is pressed. The µP 
determines from the voltage on these lines which key is pressed and sends the information to the 
host radio.
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 R0880. Transistor 
Q0871 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 Q0871 and the resulting high level at µP port PA2  
						

							2-12THEORY OF OPERATION
informs the µP about the pressed PTT button. The µP will inform the host radio about any status 
change on the PTT IRDEC line via SBEP bus.
When line PTT IRDEC is connected to FLT A+ level, transistor Q0851 is switched on through diode 
VR0851 and thereby pulls the level on line ON OFF CONTROL to FLT A+ level. This switches on the 
radio and puts the radio’s µP in bootstrap mode. Bootstrap mode is used to load the firmware into 
the radio’s flash memory (See controller sub section for more details).
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 R0883. Transistor 
Q0872 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 R0883 and the resulting high level at µP port PA1 
informs the µP about the closed hang up switch. The µP will inform the host radio about any status 
change on the HOOK line via SBEP bus.
4.10 Speaker (Remote Mount Configuration only)
The remote mount controlhead contains a speaker for the receiver audio. The receiver audio signal 
from the differential audio output of the audio amplifier located on the radio’s controller is fed via 
connector J0801-10,11 to the speaker connector P0801 pin 1 and pin 2. The speaker is connected 
to the speaker connector P0801. The controlhead speaker can be disconnected if only an external 
speaker, connected on the accessory connector, should be used. If the controlhead is mounted 
directly on the radio, an external speaker is required.
4.11 Electrostatic Transient  Protection
Electrostatic transient protection is provided for the sensitive components in the controlhead by 
diodes VR0811 - VR0814. The diodes limit any transient voltages to tolerable levels. The associated 
capacitors provide Radio Frequency Interference (RFI) protection. 
						

							Chapter 3
TROUBLESHOOTING CHARTS
1.0 Controlhead GM140/340/640 Troubleshooting Chart
1.1 On/Off 
Radio can not be switched on via ON/OFF Volume 
NO
YES
YES
NO R0823 Pin TAB
= 5V ?
R0823 Pin TAB1
when pressed
= 5V ?Check / Replace 
Volume Pot R0823
Check / Replace
R0822 / VR0822 / 
D0822
NO
YES
J0801 Pin 2
> 10V ?Check / Replace
Q0821
Check / Replace
Q0822 / R0821
YES
NO
J0801 Pin 2
=5V ?Check / Replace
D0821 / R0852
Press and hold
On/Off Volume Knob 
						

							3-2TROUBLESHOOTING CHARTS
1.2 Microprocessor 
Power Up Alert Tone is OK but volume knob 
does not operate and no indicator is on
NO
YES
YES
NO
YES
NO
YES NO
YES
EXTAL
U0831 Pin 31
= 8.00 MHz ?
RESET
TP0833
= HIGH ?Check / Replace
C0833 / R0832 / U0831
Check radio controller Data Signal
on J0801 Pin 5
BUS+ ?
Data Signal 
on TP0836
SCI_RX ?
NO
Data Signal
on TP0837
SCI_TX ?
Check / Replace
R0831 / U0833 / U0831
Check / Replace
R0837 / R0836
Check / Replace
U0831
Check / Replace
D0831 / R0838
Measure with scope 
while rotating Volume  
						

							Controlhead GM160/360/660 Troubleshooting Flow Chart 3-3
2.0 Controlhead GM160/360/660 Troubleshooting Flow Chart
2.1 On/Off 
Radio can not be switched on via ON/OFF Volume Knob
NO
YES
YES
NO
R0823 Pin TAB
= 5V ?
R0823 Pin TAB1
when pressed
= 5V ?Check / Replace 
Volume Pot R0823Check / Replace
R0822 / VR0822 /
D0822 / C0822
NO
YESJ0801 Pin 2
> 10V ?Check / Replace
Q0821
Check / Replace
Q0822 / R0821
YES
NOJ0801 Pin 2
=5V ?Check / Replace
D0821 / R0852
Press and hold
On/Off Volume Knob 
						

							3-4TROUBLESHOOTING CHARTS
2.2 Microprocessor
Power Up Alert Tone is OK but volume knob does 
not operate and no indicator is on
NO
YES
YES
NO
YES
NO
YES NO
YES
EXTAL
U0831 Pin 31
= 8.00 MHz ?
RESET
TP0833
= HIGH ?Check / Replace
C0833 / R0832 / 
Check radio controller Data Signal
on J0801 Pin 5
BUS+ ?
Data Signal
on TP0836
SCI_RX ?
NO
Data Signal
on TP0837
SCI_TX ?
Check / Replace
R0831 / U0833 / U0831
Check / Replace
R0837 / R0836
Check / Replace
U0831
Check / Replace
D0831 / R0838
Measure with scope while 
rotating Volume Pot 
						

							Controlhead GM160/360/660 Troubleshooting Flow Chart 3-5
2.3 Display
Power Up Alert Tone is OK, volume knob does operate,
indicator/backlight is on but nothing on display
YES
NO
YES
NO
V5 (against 5V)
TP0973 between
-6V and -7V ?
Activity on
Address & Data lines
A0 / D0..D7 / CS1
of U0971?Check for shortage
U0831 / U0971
Check LCD Assembly
Check / Replace
C0971 / C0973 / R0972
R0973 / R0974 / U0971 
						

							3-6  TROUBLESHOOTING CHARTS
2.4  Backlight 
Power Up Alert Tone is OK, volume knob does operate,
YES
NO
Check for shortage
YES
NO
Check / Replace