CPU (LSI1: MSM6755B-17)
The CPU reads sound data from the ROM in accordance with the pressed key and the selected tone; the CPU can read rhythm data simultaneously when a rhythm pattern is selected. Then it provides the left and the right channels’ waveforms separately, by converting the data into the waveforms with two
Pin No. | Terminal | In/Out | Function |
1 | MA14 | Out | Address bus |
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2, 3 | NCO | — | Not used |
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4 ~ 19 | MA0 ~ MA13 | Out | Address bus |
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13 | MRDB | Out | Read enable signal |
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17 | MCSB | — | Not used |
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20 ~ 27 | MD0 ~ MD7 | In/Out | Data bus |
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28, 29 | NC1, NC2 | — | Not used |
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30 | DGND | In | Ground (0 V) source |
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31 | DVCC | In | +5 V source |
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32, 33 | XTLO, XTLI | In/Out | 20 MHz clock input/output |
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34 | NC3 | — | Not used |
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35 | RSTB | In | Reset signal input |
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36 | P24/RXD | — | Not used. Connected to +5 V. |
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37 | P25/TXD | — | Not used |
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38 | NMI | In | Power ON signal input. Connected to +5 V. |
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39 | APO | Out | APO (Auto Power Off) signal output |
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40 | NC4 | — | Not used |
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41 | REFH | Out | Terminal for the internal DAC |
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42, 43 | NC5, NC6 | — | Not used |
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44 | DAOR | Out | Right channel sound waveform output |
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45 | NC7 | — | Not used |
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46 | AVdac | In | +5 V source for the internal DAC |
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47 | DAOL | Out | Left channel sound waveform output |
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48 | REFL | Out | Terminal for the internal DAC and ADC |
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49 | AGdac | In | Ground source for internal DAC |
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50 | AGadc | In | Ground source for internal ADC |
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51 | ANI | In | APO cancellation signal |
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52 | AVadc | In | +5 V source for the internal ADC |
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53 | NC8 | — | Not used |
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54 | MOD0 | In | Mode selection terminal. Connected to +5 V. |
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55, 56 | MOD1, MOD2 | In | Mode selection terminal. Connected to ground. |
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57 | P40 | — | Not used |
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58 ~ 64 | KI0/P30 ~ KI7/P36 | In | Terminals for key/button input signal |
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65 | KI7/P37 | — | Not used |
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66 ~ 73 | KO0/P50 ~ KO7/P57 | Out | Terminals for key scan signal |
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— 4 —
