Sensing Of Vox Operating; Microprocessor Power-On Reset Routine; Microprocessor 7.3728 Mhz Clock; Battery Indicator - Motorola EP350 Service Manual

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4.3.5

Sensing of VOX operating

Port PTT2 (Pin 68) is used to detect the presence of VOX operating when externally connected
accessories with VOX enabled. When port PTT2 is low, the VOX will start to operate.
4.3.6

Microprocessor Power-on reset Routine

On power-up, the microprocessor is held in reset until the digital 3.3V regulator (U506 Pin 4)
provides a stable supply voltage. Once the digital supply reaches steady state and releases the reset
line (U107 Pin 2), the microprocessor begins to start up. After reset release by all circuit, the software
within the microprocessor begins executing port assignment, RAM checking, and initialization.
4.3.7

Microprocessor 7.3728 MHz Clock

The 7.3728 MHz clock signal (Pin 13, X-in) is provided from the FL101.
4.3.8

Battery indicator

Various battery types are available having different capacities. The radio can select different battery
type by FPP (Front Panel Programming) or CPS. A voltage divided by R153 and R154. And
EEPROM have a data for each battery types.
Controller Theory of Operation: Microprocessor Circuitry