Casio CTK-680 Service Manual page 14

LED DRIVING
IC301
BA612
LED Driver
LC1
LC8
LG
RESET CIRCUIT
When batteries are set or an AC adapter is connected, the reset IC provides a low pulse to the CPU. The CPU
then initializes its internal circuit.
When the power switch is pressed, the CPU receives a low pulse of POWER signal. The CPU provides APO
signal to the power supply circuit and raises RESET signal to +5 V to reset the DSP, the key controller and
the gate array.
Battery set
VDD
RESET
Reset IC
IC13
RH5VL36AA
POWER
From power switch
To power supply circuit
LVDD
La ~ Lg, Lp
Q15 ~ Q18
LED Driver
UPD65611GB-019-3BA
KO0 ~ KO3, KO5
Gate array
VDD
CPU
LSI14
HD6433294A33F
-NMI
APO
P42
LD0 ~ LD7
IC17
P40
P41
DVDD
Gate Array
LSI17
UPD65611GB-019-3BA
-RESET
VDD
Working Storage RAM
LSI15
TC55257DFL-70L
— 14 —
CPU
LSI14
HD6433294A33F
DVDD
DSP
LSI11
HG51B155FD-1
DVDD
Key Controller
LSI16
HG52E35P