Reset Circuit; Control Block Diagram - Kenwood TK-80 Service Manual

SELECTIVE CALL UNIT
DTMF
MIC SW
DTMF
decoder
IC3
CONTROL UNIT
DATA BUS
Slide
SW
S1,S3
D7~D9
D12~D15
Internal AT control
Selective
Outside AT control
call
decoder
IC1,IC2
Low voltage
D4,D5,Q1,Q2

5-2. Reset circuit

IC3 monitors Vcc applied to the microcomputer. If the
voltage falls below 2.15V, the IC outputs a reset signal ("L")
to the microcomputer and the CPU initializes all internal data
(including memory channel No. 11 to 80). The reset signal is
not output when the power is turned on or off or 14V is
turned on or off. It is output when the battery voltage level
goes low and 14V is turned on or off.
C34 generates the signal width (td) required to reset the
microcomputer (Fig. 9).
CIRCUIT DESCRIPTION
LCD ASSY
AT, SCAN
LCD
MENU
MODE
DATA
LCD
SW
driver
Expand I/O
IC7
Enable
VCO select
uart rx
Reset
reset
IC3
int
detection
EEPROM
IC6
PC control
Fig. 8 Control block diagram
Rotary
encoder
SQL
CLARI
Power
VR Buffer
SW
int a/d timer
(int) (PWM)
CPU
IC5
uart
int
Buffer Buffer
IC8 Q3~Q6
BOVR
Outside
IF-232C
AT
Serial/Parallel
FINAL UNIT
D1
5V
Vcc
4.35V
2.15V
td
Fig. 9 Reset circuit
TK-80
AT UNIT
Internal
AT
POD1,POD2
TX-RX UNIT
timer a/d
PLL/DDS
IC500~IC502
Serial/Parallel
IC10,IC15,IC16
DAC
IC13
a/d SM, VSFM, VSRM
SS, KEY, KYS
IC4
67
Vcc
3
IC5
CPU
1 26
2
IC3
RESET
Reset IC
7
RESET RESET
17