Cpu And Peripheral Circuits - Alinco DJ-175 Service Manual

4) CPU and Peripheral Circuits

1. LCD Display Circuit
The CPU turns ON the LCD via segment and common terminals with 1/4 the
duty and 1/3 the bias, at the frame frequency is 112.5Hz.
2. Display Lamp Circuit
When the LAMP key is pressed, "L" is output form pin 67 of CPU ( IC113) to
the bases of Q140. Q140 then turn ON and the LEDs (D128 and D129) light.
3. Reset and Backup
When the power form the DC jack or external battery increases from Circuits
0V to 2.5 or more, " H " level reset signal is output form the reset IC (IC108) to
pin 6 of the CPU (IC113), causing the CPU to reset. The reset signal, however,
waits at 100, and does not enter the CPU until the CPU clock (X104) has
stabilized.
4. S (Signal) Meter Circuit
The DC potential of pin 12 of IC103 is input to pin 83 of the CPU (IC113),
converted from an analog to a digital signal, and displayed as the S-meter
signal on the LCD.
5. DTMF Encoder
The CPU (IC113) is equipped with an internal DTMF encoder. The DTMF
signal is output from pin 71, through IC112 (Low-pass filter), and then through
the microphone amplifier (IC110), and is sent to the varicap of the VCO for
modulation. At the same time, the monitoring tone passes through the AF
circuit and is output form the
6. TONE Encoder
The CPU (IC113) is equipped with an internal tone encoder. The tone signal
(67.0 to 250.3Hz ) is output from pin 70 of the CPU to the 21.25MHz reference
oscillation (X102) of the PLL reference oscillator.
7. DCS Encoder
The CPU (IC113) is equipped with an internal DCS code encoder. The code
(023 to 754) is output from pin 70 of the CPU to the 21.25MHz reference
oscillation (X102) of the PLL reference oscillator.
speaker.