Professional Radio
GM Series
Controller
Service Information
Issue: September 2000
ii
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Table of Contents
Chapter 1 THEORY OF OPERATION
1.0 Controller Circuits ................................................................................................1-1
1.1 Overview.........................................................................................................1-1
1.2 General...........................................................................................................1-1
1.3 Radio Power Distribution................................................................................1-2
1.4 Electronic ON/OFF.........................................................................................1-3
1.5 Emergency .....................................................................................................1-4
1.6 Mechanical ON/OFF.......................................................................................1-4
1.7 Ignition............................................................................................................1-5
1.8 Microprocessor Clock Synthesizer.................................................................1-5
1.9 Serial Peripheral Interface (SPI).....................................................................1-5
1.10 SBEP Serial Interface.....................................................................................1-6
1.11 General Purpose Input/Output .......................................................................1-6
1.12 Normal Microprocessor Operation..................................................................1-7
1.13 FLASH Electronically Erasable Programmable Memory................................1-8
1.14 Electrically Erasable Programmable Memory (EEPROM)..............................1-9
1.15 Static Random Access Memory (SRAM) .......................................................1-9
1.16 Universal Asynchronous Receiver Transmitter (UART) .................................1-9
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2.0 Controller Board Audio and Signalling Circuits....................................................1-9
2.1 General - Audio Signalling Filter IC with Compander.....................................1-9
2.2 Transmit Audio Circuits ................................................................................1-10
2.3 Transmit Signalling Circuits..........................................................................1-12
2.4 Receive Audio Circuits .................................................................................1-14
2.5 Receive Signalling Circuits...........................................................................1-17
2.6 Voice Storage...............................................................................................1-18
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Chapter 2 TROUBLESHOOTING CHARTS
1.0 Controller............................................................................................................2-1
Chapter 3 CONTROLLER SCHEMATICS
1.0 Allocation of Schematics and Circuit Boards.......................................................3-1
2.0 T2 Controller .......................................................................................................3-3
3.0 T5 Controller .....................................................................................................3-10
4.0 T6/7 Controller ..................................................................................................3-19
1.0 Controller Circuits
1.1 Overview
This section provides a detailed theory of operation for the radio and its components. The main radio
is a single board design, consisting of the transmitter, receiver, and controller circuits. The main
board is designed to accept one additional option board. This may provide functions such as secure
voice/data, voice storage or signalling decoder.
A controlhead is either mounted directly or connected by an extension cable. The controlhead
contains, LED indicators, a microphone connector, buttons and dependant of the radio type, a
display and a speaker. These provide the user with interface control over the various features of the
radio.
If no controlhead is mounted directly on the front of the radio, an e xpansion board containing circuitry
for special applications can be mounted on the front of the radio. An additional controlhead can be
connected by an extension cable.
In addition to the power cable and antenna cable , an accessory cable can be attached to a connector
on the rear of the radio. The accessory cable provides the necessary connections for items such as
external speaker, emergency switch, foot operated PTT, and ignition sensing, etc
Chapter 1
THEORY OF OPERATION
1.2 General
The radio controller consists of 3 main subsections:
■
■
Digital Control
■
■
Audio Processing
■
■
Voltage Regulation.
The digital control section of the radio is based upon an open architecture controller configuration.It
consists of a microprocessor, support memory , support logic, signal MUX ICs, the On/Off circuit, and
general purpose Input/Output circuitry.
The controller uses the Motorola 68HC11FL0 microprocessor (U0101). In addition to the
microprocessor, the controller has 3 external memory devices. The 3 memory devices consist of a
32Kbyte SRAM (U0122), a 512Kbyte FLASH EEPROM (U0121), and a 16Kbyte EEPROM (U0111).
Note: From this point on the 68HC11FL0 microprocessor will be referred to as µP. References to a
controlhead will be to the controlheads with display.
1-2 THEORY OF OPERATION
16.8 MHz
Reference Clock
from Synthesizer
Recovered Audio
5V
from Synthesizer
Section (5V_RF)
To RF Section
To Synthesizer
Digital
Architecture
5V
Regulator
(5VD)
Figure 1-1 Controller Block Diagram
Mod
Out
ASFIC_CMP
SPI
Audio/Signalling
Architecture
RAM
EEPROM
FLASH
External
Microphone
Internal
Microphone
External
Speaker
Audio
PA
Internal
Speaker
µP Clock
SCI to
Accessory &
Controlhead
Connector
HC11FL0
1.3 Radio Power Distribution
The DC power distribution throughout the radio board is shown in Figure 2-1. Voltage regulation for
the controller is provided by 4 separate devices; U0651 (MC78M05) +5V, U0641 (LM2941) +9.3V,
U0611 (LM2941) SWB+ limited to 16.5V and VSTBY 5V (a combination of R0621 and VR0621). An
additional 5V regulator is located on the RF section.
The DC voltage applied to connector J0601 supplies power directly to the electronic on/off control,
RF power amplifier, 16.5V limiter, 9.3V regulator, Audio PA and 5.6V stabilization circuit. The 9.3V
regulator (U0641) supplies power to the 5V regulator (U0651) and the 6V voltage divider Q0681.
Regulator U0641 is used to generate the 9.3 volts required by some audio circuits, the RF circuitry
and power control circuitry. Input and output capacitors (C0641 and C0644 / C0645) are used to
reduce high frequency noise. R0642 / R0643 set the output voltage of the regulator. If the voltage at
pin 1 is greater than 1.3 volts the regulator output decreases and if the voltage is less than 1.3 volts
the regulator output increases. This regulator output is electronically enab led by a 0 v olt signal on pin
2. Q0661, Q0641 and R0641 are used to disable the regulator when the radio is turned off.
Voltage regulation providing 5V for the digital circuitry is done by U0651. Operating voltage is from
the regulated 9.3V supply. Input and output capacitors (C0651 / C0652 and C0654 / C0655) are
used to reduce high frequency noise and provide proper operation during battery transients. Voltage
sense device U0652 or alternatively U0653 provides a reset output that goes to 0 volts if the
regulator output goes below 4.5 volts. This is used to reset the controller to prevent improper
operation. Diode D0651 prevents discharge of C0652 by negative spikes on the 9V3 voltage.
Transistor Q0681 and resistors R0681 / R0682 divide the regulated 9.3V down to about 6 volts. This
voltage supplies the 5V regulator, located on the RF section. By reducing the supply voltage of the
regulator, the power dissipation is divided between the RF section and the controller section.
Controller Circuits 1-3
The voltage VSTBY, which is derived directly from the supply voltage by components R0621 and
VR0621, is used to buffer the internal RAM. C0622 allows the battery voltage to be disconnected for
a couple of seconds without losing RAM parameters. Dual diode D0621 prevents radio circuitry from
discharging this capacitor. When the supply voltage is applied to the radio, C0622 is charged via
R0621 and D0621. To avoid that the µP enters the wrong mode when the radio is switched on while
the voltage across C0622 is still too low, the regulated 5V charges C0622 via diode D0621.
J0601
13.2V
PASUPVLTG
FLT_A+
PA, Driver
Antenna Switch
16.5V
Limiter
ON / OFF
Control
9.3V
Regulator
Audio PA
5.6V
20 Pin Connector
SWB+
Ignition
Emergency
ON/OFF
Temp Sense
RX RF Amp
Accessories
9V3
PCIC,
TX Amp
IF Amp
VSTBY
Controlhead
12 Pin Connector
F0401
FLT_A+
5VD
6V
Regulator
5V
Regulator
5VD
MCU
µP, RAM,
FLASH & EEPROM
Option Board
40 Pin Connector
5V
Regulator
ASFIC_CMP
5V_RF
5V/
VDDA
FRACTN
VCOBIC
Figure 2-1 DC Power Distribution Block Diagram
The voltage INT SW B+ from switching transistor Q0661 provides power to the circuit controlling the
audio PA output. The voltage INT SW B+ voltage is monitored by the µP through voltage divider
R0671 / R0672 and line BATTERY VOLTAGE. Diode VR0671 limits the divided voltage to 5.6V to
protect the µP.
Regulator U0611 is used to generate the voltage for the switched supply voltage output (SWB+) at
the accessory connector J0501 pin 13. U0611 is configured to operate as a switch with voltage and
current limit. R0611 / R0612 set the maximum output voltage to 16.5 volts. This limitation is only
active at high supply voltage levels. The regulator output is electronically enabled by a 0 volt signal
on pin 2. Q0661, Q0641 and R0641 are used to disable the regulator when the radio is turned off.
Input and output capacitors (C0603 and C0611 / C0612) are used to reduce high frequency noise.
Diode VR0601 acts as protection against transients and wrong polarity of the supply voltage.
Fuse F0401 prevents damage of the board in case the FLT A+ line is shorted at the controlhead
connector.
1.4 Electronic ON/OFF
The radio has circuitry which allows radio software and/or external triggers to turn the radio on or off
without direct user action. For example, automatic turn on when ignition is sensed and off when
ignition is off.
Q0661 is used to provide INT SW B+ to the various radio circuits and to enable the voltage
regulators via transistor Q0641. Q0661 contains an pnp and an npn transistor and acts as an
electronic on/off switch. The switch is on when the collector of the npn transistor within Q0661 is low.
When the radio is off the collector is at supply voltage level. This effectively prevents current flow
1-4 THEORY OF OPERATION
from emitter to collector of the pnp transistor. When the radio is turned on the voltage at the base of
the npn transistor is pulled high and the pnp transistor switches on (saturation). With voltage INT
SWB+ now at supply voltage le vel, transistor Q0641 pulls pin 2 of the voltage regulators U0611 and
U 0641 to ground level and thereby enables their outputs.
The electronic on/off circuitry can be enabled by the microprocessor (through ASFIC CMP port
GCB2, line DC POWER ON), the emergency switch (line EMERGENCY CONTROL), the
mechanical On/Off/V olume knob on the controlhead (line ON OFF CONTR OL), or the ignition sense
circuitry (line IGNITION CONTROL). If any of the 4 paths cause a low at the collector of the npn
transistor within Q0661, the electronic "ON" is engaged.
1.5 Emergency
The emergency switch (J0501 pin 9), when engaged, grounds the base of Q0662 via line
EMERGENCY CONTROL. This switches Q0662 off and resistor R0662 pulls the collector of Q0662
and the base of Q0663 to levels above 2 volts. Transistor Q0663 switches on and pulls the collector
of the npn transistor within Q0661 to ground level and thereby enables the voltage regulators via
Q0641. When the emergency switch is released R0541 pulls the base of Q0662 up to 0.6 volts. This
causes the collector of transistor Q0662 to go low (0.2V), thereby switching Q0663 off.
While the radio is switched on, the microprocessor monitors the voltage at the emergency input on
the accessory connector via pin 60 and line GP5 IN ACC9. Three different conditions are
distinguished, no emergency, emergency, and open connection to the emergency switch. If no
emergency switch is connected or the connection to the emergency switch is broken, the resistive
divider R0541 / R0512 will set the voltage to about 4.7 volts. If an emergency switch is connected, a
resistor to ground within the emergency switch will reduce the voltage on line GP5 IN A CC9 to inf orm
the microprocessor that the emergency switch is operational. An engaged emergency switch pulls
line GP5 IN ACC9 to ground level. Diode D0179 limits the voltage to protect the microprocessor
input.
While EMERGENCY CONTROL is low , INT SW B+ is on, the microprocessor starts ex ecution, reads
that the emergency input is active through the voltage level of line GP5 IN ACC9, and sets the DC
POWER ON output of the ASFIC CMP pin 13 to a logic high. This high will keep Q0661 and Q0641
switched on. This operation allows a momentary press of the emergency switch to power up the
radio. When the microprocessor has finished processing the emergency press, it sets the DC
POWER ON line to a logic 0. This turns off Q0661 and the radio turns off. Notice that the
microprocessor is alerted to the emergency condition via line GP5 IN ACC9. If the radio w as already
on when emergency was triggered then DC POWER ON would already be high.
1.6 Mechanical ON/OFF
This refers to the typical on/off/volume knob, located on the controlhead, and which turns the radio
on and off.
If the radio is turned off and the on/off/volume knob is pressed, line ON OFF CONTROL (J0401 pin
11) goes high and switches the radio’s voltage regulators on as long as the button is pressed. The
microprocessor is alerted through line ON OFF SENSE (U0101 pin 6) which is pulled to low by
Q0110 while the on / off / volume knob is pressed. In addition, an interrupt is generated at µP pin 96.
The µP asserts line DC POWER ON via ASFIC CMP, pin 13 high which keeps Q0661 and Q0641,
and in turn the radio, switched on. When the on/off/volume knob is released again the controlhead
informs the µP via SBEP bus about the knob release. (See SBEP Serial Interface subsection for
more details). This informs the µP to keep the radio switched on and continue with normal operation.
If the on/off/volume knob is pressed while the radio is on, the controlhead informs the µP via SBEP
bus about the knob status. (See SBEP Serial Interface subsection for more details). After a short
delay time the microprocessor switches the radio off by setting DC POWER ON to low via ASFIC
CMP pin 13.
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