— 4 —
CPU (LSI1: MSM6521-11)
Containing a sound data ROM and a DAC (Digital to Analog Converter), the CPU provides sound wave-
form in accordance with the pressed key and selected tone. The CPU also drives LEDs in the illuminated
keyboard directly. The following table shows the pin functions of LSI1.
Filter Block
Since the sound signal from the CPU is a stepped waveform, the filter block is added to smooth the
waveform.
Pin No.
Terminal
In/Out
Function
1 ~ 7
LY1 ~ LY7
Out
Keyboard LED drive signal output
8
LVDD1
In
+5V source for the built-in LED driver
9
LGND2
In
Ground (0V) source for the built-in LED driver
10 ~ 13
LX0 ~ LX3
Out
Keyboard LED drive signal output
14 ~ 17
LX4 ~ LX7
Out
Not used.
18
LVDD2
In
+5V source for the built-in LED driver
19
GND2
In
Ground (0V) source
20, 21
COSI, COSO
In/Out
21.725 MHz clock pulse input/output
22
VDD
In
+5V source
23
GND1
In
Ground (0V) source
24 ~ 26
TEST1 ~ TEST3
In
Not used. Connected to ground.
27
RESET
In
Reset signal input. Power OFF: 0V, Power ON: +5V
28
AVDD
In
+5V source for the built-in DAC
29
OUT
Out
Sound waveform output
30
AGND
In
Ground (0V) source for the built-in DAC
31 ~ 38
KI0 ~ KI7
In
Input terminal for keys and switches
39 ~ 46
KO0 ~ KO7
Out
Key and switch scan signal input
47 ~ 58
Not used.
59
LGND1
In
Ground (0V) source for the built-in LED driver
60
LY0
In
Keyboard LED drive signal output
AVDD
AG
AG
AG
C11
C12
T2
2SC1740SQ
AG
C9
R1
R11
R30
C10
R12
R13
R14
