Motorola GM950E Service Manual page 40

Controller
2.0 Controller
2.1 General
The radio controller consists of 4 main subsections:
Digital Control
Audio Processing
Power Control
Voltage Regulation
The digital control section of the radio board is based upon a closed architecture controller
conÞguration.
The digital section consists of a microprocessor, support memory, support logic, signal MUX ICs, the
On/Off circuit, and general purpose Input/Output circuitry.
The closed architecture controller uses the Motorola 68HC11E9 (U0101) for a GM950E radio and
the 68HC11E20 for a GM950i radio. In this conÞguration RAM and ROM are contained within the
microprocessor itself. The only external memory device in the closed architecture controller is an
EEPROM (2KByte for GM950i).
Note: From this point on the 68HC11E9 or E20 microprocessor will be referred to as E9/20mP or
mP. References to a Control Head will be to radio model A3 (Display radio).
2.2 Voltage Regulators
Voltage regulation for the controller is provided by 3 separate devices; U0631 (LP2951CM) +5V,
U0601 (LM2941T) +9.3V, and UNSW 5V (a combination of R0621 and VR0621). An additional
regulator is located in the RF section.
Voltage regulation providing 5V for the digital circuitry is done by U0631. Input and output capacitors
(C0631/0632 and C0633-0635) are used to reduce high frequency noise and provide proper
operation during battery transients. This regulator provides a reset output (pin 5) that goes to 0 volts
if the regulator output goes out of regulation. This is used to reset the controller to prevent improper
operation. Diode D0631 prevents discharge of C0632 by negative spikes on the 9V3 voltage
Regulator U0601 is used to generate the 9.3 volts required by some audio circuits, the RF circuitry
and power control circuitry. Input and output capacitors (C0601-0603 and C0604/0605) are used to
reduce high frequency noise. R0602/R0603 sets 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 disabled by a 0 volt signal on
pin 2. Q0601 and associated circuitry (R0601/0604/0605 and C0606) are used to disable the
regulator when the radio is turned off.
UNSW 5V is only used in a few areas which draw low current and requires 5 V while the radio is off.
UNSW 5V CL is used to buffer the internal RAM. C0622 allows the battery voltage to be
disconnected for a couple of seconds without losing RAM parameters. Diode D0621 prevents radio
circuitry from discharging this capacitor.
4-2 Theory of Operation