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2.2.1.3
Audio circuit
2.2.1.3.1
RX Audio
KRK-14H has two RX Audio input channels, AFIA+/- and AFIB+/-. And the MPU selects the one of the two channels, and input it to
codec IC (IC17). (The channel to use is notified by serial communication from RF Deck.)
The codec IC adjusts RX Audio signal amplitude equal to the value of selected volume step, and output it. That output signal is con-
verted to balanced signal by operational amplifier (IC19). And converted signal goes to Class-D audio amplifier (IC25). The audio am-
plifier is controlled to shutdown or power-up, by MPU.
2.2.1.3.2
TX Audio
KRK-14H has two microphone input channels. One is connected to Basic type panel (KCH-19), other is connected to external interface
connector (CN2). Two microphone signals are selected by analog multiplexer IC (IC20), and inputted to microphone amplifier. The
microphone amplifier consists of operational amplifier and AGC. And its output is connected to Codec IC. The total gain of amplifiers
in Codec IC is set to 0dB. The output signal of codec IC is converted to balanced signal by operational amplifier (IC13). The converted
signals are switched by analog switch IC (IC11, IC12), and output to either MICA+/- or MICB+/-. The output channel is notified from
RF Deck by serial communication.
2.2.1.4
Control circuit
The control circuit consists of MPU (IC16) and its peripheral circuits. IC16 mainly performs the followings;
(1) Serial communication between RF deck and KRK-14H
(2) Controlling the audio circuits including codec IC
(3) Controlling the display
2.2.1.4.1
MPU
The MPU is 32bit RISC processor, equipped with peripheral functions. The maximum operating clock of MPU is 288MHz, and power
source are 3.3V/ 1.8V/ 1.2V DC. The MPU controls the flash memory, Mobile DDR, the audio circuits, the Key detection IC which is
on Basic type panel, external I/O circuit, and the display (LCD).
2.2.1.4.2
Memory Circuit
Memory circuit consists of the MPU and the Mobile DDR (IC23), the flash memory (IC29). The flash memory has capacity of 256Mbit
that contains the program for the MPU and stores the data. That program can be easily updated from external devices. The Mobile
DDR has capacity of 512Mbit. The MPU copies the program from the flash memory to the Mobile DDR. The MPU uses the Mobile
DDR as a work area.
2.2.1.4.3
LCD control interface
The MPU controls LCD which is in Basic type panel (KCH-19) through the panel interface connector (CN37). LCD is controlled by
parallel bus with 16bit data width.
2.2.1.4.4
Key detection
The MPU can detect the keys of Basic type panel (KCH-19). In the Basic type panel, the keys are connected to I/O expander IC which
has key matrix function. When the key was pushed, I/O expander IC scans which key is pushed. Then an interrupt occurs for a MPU
from an I/O expander IC. The MPU reads the registers of I/O expander IC after an interrupt occurs, and checks which key is pushed.
2.2.1.4.5
External I/O
KRK-14H has external interface connector (CN2). That interface has two output and two input terminals. The output terminal is open
collector type. The input terminal has level shift circuit, it permits input the 5V signal.
2.2.2 KRK-15B
2.2.2.1
Overview
KRK-15B is an optional unit designed to separate the Mobile transceiver and Basic type panel (KCH-19) by remote control cable (KCT-
71). KRK-15B communicates with Mobile transceiver in a serial bus and controls Basic type panel. This unit consists of a power supply
circuit, audio circuit, and control circuit.
2.2.2.2
Power supply circuit
54M (5.4V DC Power) is supplied from Mobile transceiver via CN1. 54M is power source of IC2 (CAN Transceiver) and IC3 (33D, 3.3V
regulator). 33A (3.3V DC Power) is power source of Audio circuits.
33M (3.3V DC Power) is supplied from Mobile transceiver via CN1. 33M is power source of IC7 (I/O Expander).
SB (Switched +B Power) is supplied from Mobile transceiver via CN2. SB is power source of Control head interface kit (KRK-14H).
1-6 (No.RA021<Rev.001>)
CN1
54M
IC3
3.3V AVR
33M
CN2
SB
Fig.1 power supply circuit
IC2 CAN transceiver
33A
Audio circuits
I/O Expander IC
CN3 Separate I/F
CN4 Separate I/F
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