Casio CTK-500 Service Manual page 7

FIlter Block
Since the sound signall from the CPU is a stepped waveform, the filter block is added to smooth the
waveform.
To main volume
Initial 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.
S8053ANO
Power On/Off Circuit
When the power switch is turned on, a low level differential pulse is provided to terminal MI of the CPU.
Upon receipt of the pulse, the CPU starts the power ON sequence and raises the APO signal to +5 V.
When the switch is off, on receiving the KO11 signal at terminal KI0, the CPU drops the APO signal to
ground level to shut down power.
VDD
Power Switch
OFF
ON
OFF
ON
VDD
2SC3112B
AG
AG
Battery set
VDD
Reset IC
IC4
VDD
KI0
KI1
KO11
10K
10K 6.2K
C562(H)
AG
CPU
MSM6626-01
LSI1
RESET
ON
MI
— 5 —
From the CPU
CPU
KO18
MSM6626-01
APO signal
LSI1
OFF: 0V
ON: +5 V