(No.RA003)1-72.1.5 Control CircuitThe control consists of the MCU (IC710) and its peripheral circuits. It controls the TX-RX unit. IC710 mainly performs the following;(1) Switching between transmission and reception via the PTT signal input.(2) Reading channel information, frequency, and program data from the memory circuit.(3) Sending frequency program data to the PLL.(4) Controlling squelch on/off via the DC voltage from the squelch circuit.(5) Controlling the audio mute circuit via the decode data input.(6) Transmitting tone and encode data.2.1.5.1 Frequency Shift CircuitThe MCU (IC710) and baseband IC (IC705) operate at a clock frequency of 19.2MHz.This oscillator frequency can be shifted by pin 8 of the MCU (IC710). When pin 8 is set to high, the beat shift function is ON.A beat sound may be able to be evaded from generation if “Beat Shift” is set to ON when it is generated in the internal spurious trans-mission modulated sound of the transceiver.Fig.7 Frequency shift circuit2.1.5.2 Memory CircuitThe Memory circuit consists of the MCU (IC710) and EEPROM (IC700). The EEPROM has a capacity of 64K-bit and stores the chan-nel information, the last channel data, the scan on status, and other parameters.EEPROMNote:The EEPROM stores tuning data (Deviation, Squelch, etc.).Realign the transceiver after replacing the EEPROM.2.1.5.3 Low Battery WarningThe battery voltage is monitored by the MCU (IC710 pin 33: BATT). When the battery voltage falls below 6.4V approximately, the redLED blinks, notifying the operator that it is time to replace the battery (When “Always” option (default setting) under the Battery Warningfunction in the FPU is selected).If the battery voltage falls below 5.8V approximately, the transceiver does not transmit and a warning tone beeps when the PTT switchis pressed (When the Battery Warning Tone is selected in the FPU).2.1.5.4 Key InputKeys and channel selector circuit.The signal from the keys and channel selector are directly input to the MCU, as shown in Figure 8.Fig.8 Key inputIC705Baseband ICH: OFFL: ON39XTALIC710MCU8 12BSHIFT XINX2TCXO19.2MHzIC713CLK AMP13 264EN4EN3SelectorIC710MCU Side1Side2PTTSWEN2EN1 Side2Side1PTT66646563596061
