KENWOOD TK270GN
Manual de Servicio

TK-260G/(N)/270G/(N)
CIRCUIT DESCRIPTION
6. Control Circuit
The control circuit consists of a microprocessor (IC13) and its peripheral circuits. It controls the TX-RX unit and transfers data to and from the display unit. IC13 mainly performs the following: (1) Switching between transmission and reception by the PTT signal input. (2) Reading system, group, frequency, and program data from the memory circuit. (3) Sending frequency program data to the PLL. (4) Controlling squelch on/off by the DC voltage from the squelch circuit. (5) Controlling the audio mute circuit by the decode data input. (6) Transmitting tone and encode data.

3) Low battery warning
The battery voltage is monitored by the microprocessor (IC13). When the battery voltage falls below the voltage set by the Low Battery Warning adjustment, the LED flashes red to notify the operator that it is time to replace the battery. If the battery voltage falls even more (approx. 5.8V), a beep sounds and transmission is stopped. Low battery warning The red LED flashes during transmission. The red LED flashes and a continuous beep sounds while PTT is pressed. Battery condition The battery voltage is low but the transceiver is still usable. The battery voltage is low and the transceiver is not able to make calls.

1) Frequency shift circuit
The microprocessor (IC13) operates at a clock of 9.8304MHz. This oscillator has a circuit that shifts the frequency by BEAT SHIFT SW (Q31).

2) Memory circuit
Memory circuit consists of the CPU (IC13) and a flash memory (IC12). A flash memory has a capacity of 2M bits that contains the transceiver control program for the CPU and data such as transceiver channels and operating features. This program can be easily written from an external device. Data, such as DTMF memories and the operating status, are programmed into the EEPROM (IC10).

q

Flash Memory Note : The flash memory holds data such as written with the FPU (KPG-56D), and firmware program (User mode, Test mode, Tuning mode, etc.). This data must be rewritten when replacing the flash memory. EEPROM Note : The EEPROM stores tuning data (Deviation, Squelch, etc.). Realign the transceiver after replacing the EEPROM.
IC13 CPU IC10 EEPROM
q

FLASH IC12

Fig. 9 Memory circuit

21