4-6 Controller Theory of Operation: Microprocessor Circuitry
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.
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