Kenwood NX-740H Service Manual page 13

2.4.5 Control Circuit
The MCU carries out the following tasks:
(1) Controls the FM IC (IC501).
(2) Controls the baseband IC (IC709).
(3) Controls the PLL (IC2) & TX/RX outputs.
(4) Controls IO expender through I2C level converter.
(5) Controls the display unit.
2.4.5.1 Memory Circuit
The transceiver has an 256k-bit EEPROM (IC716). The EE-
PROM contains adjustment data. The MCU (IC714) controls the
EEPROM through three serial data lines.
2.4.5.2 Display Circuit
The MCU (IC714) controls the Display 7-segment LED and
LEDs.
When power is on, the MCU will use the MBL line to control the
key backlight LEDs.
When the transceiver is busy, the GLED line goes high, Q1 turns
on and the green LED (D23) lights after Q4 turn on. In transmit
mode, the RLED line goes high, Q2and Q8 turns on and the red
LED (D23) lights.
BLED will be set high when the function select (FPU setting) is
on, Q6 turn on and the blue LED (D22) lights.
The dimmer function is controlled by the switch Q5. The LED
driver (IC1) controls the functions of the 7-segment LED through
the LEDI, LECE, LECL, LELH lines from the MCU.
PDN
RSTN
CSN
IC501
FM IC
SCLK
SDATA
IC2
PLL IC
C.DATA
R.DATA
SCLK
IC714 IRQ
MCU
CSN
IC1
LED Driver
Display unit
Fig.8 Control circuit
IC714
MCU
IC714
MCU
IC709
Baseband
2
I C level IO
converter expender
IC700 IC702
EEP_DATAO
EEP_CLK
IC716
EEP_DATAI
EEPROM
EEP_CS
EEP_WP
Fig.9 Memory circuit
LEDM
Q5
SW
Display
LEDI
7-segment
LECE
IC1
LECL LED
driver
LELH
D1~D5
Key backlight
MBL
Q3 Q4
SW SW
GLED
Q1 Q7
SW SW
RLED
Q2 Q8
SW SW
D22
BLED
Q6
SW
Fig.10 Dsplay circuit
(No.RA010<Rev.001>)1-13
D23