(No.RA062<Rev.001>)1-7
2.2.2.2 KRK-19B
54M (5.4V DC Power) is supplied from the Mobile transceiver via CN1. 54M is the power source of IC2 (CAN Transceiver) and IC3
(33A, 3.3V regulator). 33A (3.3V DC Power) is the power source of the Audio circuits.
32M (3.3V DC Power) is supplied from the Mobile transceiver via CN1. 32M is used for I/O control of IC2.
SB (Switched +B Power) is supplied from the Mobile transceiver via CN1. SB is the power source of the KRK-18H.
Fig.2 Power supply diagram
2.2.3 Audio circuit
2.2.3.1 RX Audio
The RX audio signal is controlled of the amplitude according to the volume setting and amplified by the AF power amplifier in the Mobile
transceiver. The amplified signal is going through the KRK-19B and the KRK-18H, and is connected to the speaker at the Control
Head.
2.2.3.2 TX Audio
The KRK-18H has two microphone input channels. One is connected to the Control Head (modular jack), and the other is connected
to the AUX interface connector (CN2).
These microphone signals are selected by the analog multiplexer IC (IC20), and are amplified by the microphone amplifier (IC18).
The microphone amplifier consists of the operational amplifier and AGC (Automatic Gain Control). The output signal of the microphone
amplifier is converted to the balanced microphone signal by the operational amplifier (IC13) and is supplied to the KRK-19B. The
balanced microphone signals (MIC+/-) are converted to single-end signal by IC1 on the KRK-19B. The converted signal is supplied to
the Mobile transceiver.
2.2.4 Control circuit
The control circuit consists of the MPU (IC16) and its peripheral circuits in the KRK-18H. IC16 mainly performs the followings;
(1) Serial communication with the Mobile transceiver.
(2) Controlling the microphone input path.
(3) Controlling the Control Head.
The KRK-18H has the serial communication circuit between the Mobile transceiver via the Control Head Remote unit (KRK-19B) and
the Control Head. This circuit consists of the CAN transceiver IC. This IC converts the UART signal to the CAN signal or the CAN
signal to the UART signal. To communicate between the KRK-18H and the KRK-19B, the CAN BUS is used.
2.2.4.1 MPU
The MPU is 32bit RISC processor, equipped with peripheral functions. The maximum operating clock of the MPU is 288MHz, and
power source are 3.3V/1.8V/1.2V DC. The MPU controls the Flash memory, the Mobile DDR, the Audio circuits, the Key detection IC
which is on the Control Head, the External I/O circuit, and the LCD Display.
2.2.4.2 Memory Circuit
Memory circuit consists of the MPU, the Flash memory (IC29), and the Mobile DDR (IC23).
The Flash memory is the nonvolatile memory and has capacity of 256Mbit that contains the program for the MPU and stores the data.
The program can be updated easily from PC through the Control Head. The Mobile DDR has capacity of 512Mbit. The MPU copies
the program from the Flash memory to the Mobile DDR and uses the Mobile DDR as a work area.
2.2.4.3 LCD control interface
The MPU controls the LCD which is in the Control Head through the Control Head interface connector (CN48). The LCD is controlled
by parallel bus with 8bit data width.
2.2.4.4 Key detection
The MPU can detect the keys on the Control Head. The keys are connected to the I/O expander IC in this unit which has the key matrix
function. When the key is pushed, I/O expander IC scans which key is pushed. The interrupt occurs for the MPU from the I/O expander
IC, and then the MPU reads the registers of the I/O expander IC and confirms which key is pushed.
2.2.4.5 External I/O
The KRK-18H has an external interface connector (CN2). The interface has two outputs and two inputs terminals. The output terminals
are the open drain type. The input terminals have the level shift circuit; these terminals can input the 5V signal.
CN1
Audio circuits
XC3-064
CAN transceiver
IC3
3.3V AVR
CAN transceiver
CN3
SB
54M
33A
32M
