CIRCUIT DESCRIPTION
CPU (LSI104: HD6433298A42F)
The 16-bit CPU contains a 32k-bit ROM, a 1k-bit RAM, seven 8-bit I/O ports and MIDI interfaces. The
CPU receives MIDI message and interprets it using the working storage RAM. For instance, when receiv-
ing NOTE ON message, the CPU sends the note number and its velocity to the DSP in order to produce
sound of that note.
The following table shows the pin functions of LSI104.
Pin No.TerminalIn/OutFunction
1P50/TXDN Not used
2P51/RXDIn MIDI signal input
3P52/SCKOut Reset signal output
4-RESETIn Reset signal input
5-NMIIn Power ON trigger signal input
6VCCIn +5V source
7-STBYIn Standby signal input. Connected to +5V.
8VSSIn Ground (0V) source
9, 10XTAL, EXTALIn 20MHz clock input
11, 12MD1, MD0In Mode selection input
13AVSSIn Ground (0V) source
14 ~ 20P70 ~ P76In Not used. Connected to ground.
21P77In DEMO button input signal
22AVCCIn +5V source
23P60Out LED drive signal output
24 ~30P61 ~ P67N Not used
31VCCIn +5V source
32P27N Not used
33 ~ 48A0 ~ A14Out Address bus
40VSSIn Ground (0V) source
49 ~ 56D0 ~ D7In/Out Data bus
57, 58P40, P41N Not used.
59P42Out Power ON signal output
60P43Out Read enable signal output
61P44In Write enable signal output
62P45N Not used
63P46Out Terminal for 10 MHz clock check point
64P47N Not used. Connected to +5 V source.
DIGITAL SIGNAL PROCESSOR (LSI03: HG51B155FD-1)
Upon receipt of a note number and its velocity, the DSP reads sound and velocity data from the sound
source ROM in accordance with the received MIDI message. Then it provides 16-bit serial signal to the
DAC. If a control change message or "an effect change" of exclusive message has been received, the
DSP adds the effect to the sound data using the effect RAM.
The following table shows the pin functions of LSI103.
N 10 N |
ACEC
