Maintenance Manual
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the board. And the second sheet contains logic circuitry and audio signal circuitry.
Microprocessor U501
A single microprocessor controls the all operation of the PZ series radio. All lines connect to the analog
portion of the board are first RF bypassed by RC circuits. Most of these RC circuits are physically located
as close as possible to each microprocessor pin of the board.
The microprocessor contains internal flash memory. The microprocessor normally executes the radio
software code in this Flash memory.
The Reset circuit consists of voltage detector (Q102), R101 and C117. If the input level of voltage
detector (Q102) is less than DC+2.7V, the reset circuit generates a reset signal automatically.
3.3 Volt Regulator U50
A single 3.3volt regulator U50 supplies all circuitry on the board. The regulator receives input voltage
from the battery (nominally 7.5Vdc) and fuse F50 provides protection for the main circuit.
And also the 3.3 volts for Bluetooth module, RF section and VCO can be controlled separately by
microprocessor.
Personality EEPROM
A 2048 X 8 bit EEPROM U103 stores all customer frequencies, tones and option information. Tune data
aligned with the RF section is stored for transmit high power level, transmit low power level, audio
deviation, data deviation and squelch.
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CAUTION`
If replacement of U103 personality EEPROM, contact UNIMO Technology Co., Ltd. Customer
Service to obtain programming information.
The microprocessor serially communicates with the EEPROM on the IIC_CLK AND IIC_DATA lines (or
the Inter Integrated Circuit Bus) Programming of the EEPROM is accomplished without opening the
radio by communication with the microprocessor through the Phone jack connector.
Low Battery Sense
The low battery sense circuit (R119, R121, R112, C108) monitors the current voltage state of the battery.
R545 and R547 divide the battery voltage and this low battery sense voltage is sent to microprocessor
