Casio CTK-631, Service Manual

Page: 7 / 30

— 5 —
Reset IC
IC2
RN5VD40AA
DSP
LSI2
HG51B277FB-1
VDD
Reset signal
To power supply circuit
VDD
Battery set
RESET
VDD
POWER
From power switch
NMI
APO
PLE
CPU
LSI1
GT913F(T)
SCKO
F#3 G#3 A#3 C#4 D#4 F#4 G#4 A#4 C#5 D#5 F#5 G#5 A#5
F3 G3 A3 B3 C4 D4 E4 F4 G4 A4 B4 C5 D5 E5 F5 G5 A5 B5 C6
D#3
C2 D2 E2 F2 G2 A2 B2 C3 D3 E3 B6 A6 G6 F6 E6 D6 C7
C#3 A#2 G#2 F#2 D#2 C#2 A#6 G#6 F#6 D#6 C#6
Key
Second contact (2)
First contact (1)
FI
KC
SI
Note: Each key has two contacts,
the first conatct (1) and second contact (2).
POWER SUPPLY CIRCUIT
The power supply circuit generates five voltages as shown in the following table. VDD voltage is always
generated. The others are controlled by APO signal from the CPU.
NOMENCLATURE OF KEYS
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, and clears the working storage RAM.
When the power switch is pressed, the CPU receives a low pulse of POWER signal. The CPU sends APO
signal to the power supply circuit, also sends a reset signal to the DSP.
Name Voltage For operation of
VDD +5 V CPU, Reset IC, DSP, Sound source ROM, Working storage RAM, Effect RAM
DVDD +5 V LCD driver, Power jack, Sustain jack, MIDI jack
AVDD +5 V DAC, Filter
LVDD +5.6 V LCD dirver
VCC +9 V Power amplifier, Pilot lamp