Kenwood KCH-20R Service Manual Download Page 9

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(No.RA027<Rev.001>)1-9

2.2.4.2

Memory Circuit

Memory circuit consists of the MPU and the Mobile DDR (IC23/XC3-010), the flash memory (IC29/XC3-010). 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.

2.2.4.3

Serial interface between RF deck and KCH-20R

KCH-20R is controlled by serial interface from RF deck. That interface consists of CAN transceiver (IC1/XC3-010), but that does not
support CAN protocol. UART communication is used between CAN transceiver and MPU.

2.2.4.4

LCD control interface

The MPU controls LCD through the LCD interface connector (CN57/XC3-010). LCD is controlled by parallel bus with 16bit data width.

2.2.4.5

Key detection

KCH-20R has 19 keys. The keys except the AUX key and Power key is included in key-matrix circuit. Key-matrix consists of 4 input
ports and 5 output ports. When key is pressed, the MPU starts scanning the keys and detects which key was pressed.
AUX key is connected to MPU independently. The power key is connected to RF deck through the RF deck interface connector (CN5/
XC3-011).

2.2.4.6

External I/O

KCH-20R has external interface connector (CN2/XC3-011). 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.

2.2.4.7

micro SD circuit

The micro SD card interface consists of 4bit data bus and control signals. Maximum data transfer speed is 36MHz.

2.2.5 Bluetooth Circuit

  The main component of the Bluetooth circuit is Bluetooth IC (IC12/XC3-010) and level converter circuit.
  The clocks of Bluetooth IC requires 19.2MHz for core and 32.768kHz slow clock (X1/XC3-010 and X2/XC3-010) for UART.
  Bluetooth IC communicates to the MPU (IC14/XC3-010) on the HCI UART. Interface of UART & Digital audio (I2S) between the MPU
and the Bluetooth IC, have level conversion at the level converter IC (IC13/XC3-010 and IC11/XC3-010).
The Bluetooth IC is powered by 1.8V and 3.3V which are supplied from 2 discrete external regulators (IC5/XC3-010 and IC6/XC3-
010).
TX/RX frequency is 2400-2483.5MHz (79ch Hopping, 2402-2480MHz, 1MHz step). Transmitting power is +2dBm at Bluetooth an-
tenna input.
Bluetooth antenna is surface mount chip antenna (ANT1/XC3-010), and that is connected to the Bluetooth IC through the LC filter
(L30/XC3-010).

Fig.3 Bluetooth Circuit

Frequency configuration for Bluetooth is following:
There are two LO modes: 2X and Offset LO (OSLO). 2X where LO is 2*RF_FREQ (e.g. when transmitting at 2441MHz it is at
4882MHz). OSLO where LO is at (2/3)*RF_FREQ (e.g. when transmitting at 2441MHz it is at 1627.333MHz).
In RX the 2X is always used.
In GFSK TX if power is 10dBm or more then OSLO is used.
In EDR2 TX if power is -12dBm or more then OSLO is used.
In EDR3 TX if power is -12dBm or more then OSLO is used.
Otherwise 2X is used for TX as well.

Converter

Level

Converter

UART

PCM

Antenna

IC14
MPU

19.2MHz

RF SW

D31/Q8

3.3V

IC13