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 | In/ Out | Function | ||
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1, 2 | TEST1, TEST2 |
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| Not used. Connected to ground. |
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3 | RESET |
| In | Power ON reset terminal. On: +5 V Off: 0 V | |
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4 | AVDD |
| In | +5 V sorce for the | |
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5 | OUT |
| Out | Sound waveform output | |
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6 | AGND |
| In | Ground (0 V) source for the | |
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7 | GND |
| In | Ground (0 V) source | |
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8 | COSI |
| In | 21.725 MHz clock pulse input | |
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9 | COSO |
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| Not used |
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10 | VDD |
| In | +5 V source | |
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11 ~ 18 | KI0 ~ KI7 |
| In | Input terminals from keys and switches | |
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19, 20 | KO11, KO10 |
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| Not used |
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21 ~ 30 | KO9 ~ KO0 |
| Out | Key and switch scan signal outputs | |
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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
C106R105
R104
AG
AVDD
Q101
2SC1740SQ
R2106 R107 R108
| C108 |
C107 | C109 |
AG | AG |
From CPU
Amplifier/Voltage Regulator |
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| 5V |
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VCC | NC | CONT | VREG | NC | NC | NC PRE GND | ||
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(IC101: AN8053N) | 16 | 15 | 14 | 13 | 12 | 11 | 10 | 9 |
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The right figure shows the internal block of IC101. |
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| 5V REG |
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| POWER |
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| - |
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| SP AMP |
| VREF | ||
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| + |
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| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |
| SPO | NC | SP GND | SPI | SPM | VREF | ||
— 4 —
