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CPU (LSI101: MSM6387-22)
Containing a sound data ROM and a DAC (Digital to Analog Convertor), the CPU provides sound wave-
form in accodance with the pressed key and the selected tone.
The following table shows the pin functions of LSI101.
Pin No.
Terminal
1, 2
TEST1, TEST2
3
RESET
4
AVDD
5
OUT
6
AGND
7
GND
8
COSI
9
COSO
10
VDD
11 ~ 18
KI0 ~ KI7
19, 20
KO11, KO10
21 ~ 30
KO9 ~ KO0

Filter Block

Since the sound signal from the CPU is a stepped waveform, the filter block is added to smooth the
waveform.
To power amp
Amplifier/Voltage Regulator
(IC101: AN8053N)
The right figure shows the internal block of IC101.
In/ Out
Not used. Connected to ground.
In
Power ON reset terminal. On: +5 V
In
+5 V sorce for the built-in DAC
Out
Sound waveform output
In
Ground (0 V) source for the built-in DAC
In
Ground (0 V) source
In
21.725 MHz clock pulse input
Not used
In
+5 V source
In
Input terminals from keys and switches
Not used
Out
Key and switch scan signal outputs
AVDD
C106
R105
AG
— 4 —
Function
Q101
2SC1740SQ
R2106
R107
R108
C108
AG
AG
5V
VCC
NC
CONT
VREG
16
15
14
13
5V REG
POWER
1
2
3
4
SPO
NC
SP GND PC-1
Off: 0 V
From CPU
NC
NC
NC PRE GND
12
11
10
9
-
SP AMP
VREF
+
5
6
8
7
PC-2
SPI
SPM
VREF

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