Casio ML-2 Service Manual page 6

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.
Pin No. Terminal
1 ~ 7 LY1 ~ LY7
8 LVDD1
9 LGND2
10 ~ 13 LX0 ~ LX3
14 ~ 17 LX4 ~ LX7
18 LVDD2
19 GND2
20, 21 COSI, COSO
22 VDD
23 GND1
24 ~ 26 TEST1 ~ TEST3
27 RESET
28 AVDD
29 OUT
30 AGND
31 ~ 38 KI0 ~ KI7
39 ~ 46 KO0 ~ KO7
47 ~ 58
59 LGND1
60 LY0
Filter Block
Since the sound signal from the CPU is a stepped waveform, the filter block is added to smooth the
waveform.
In/Out
Out Keyboard LED drive signal output
In +5V source for the built-in LED driver
In Ground (0V) source for the built-in LED driver
Out Keyboard LED drive signal output
Out Not used.
In +5V source for the built-in LED driver
In Ground (0V) source
In/Out 21.725 MHz clock pulse input/output
In +5V source
In Ground (0V) source
In Not used. Connected to ground.
In Reset signal input.
In +5V source for the built-in DAC
Out Sound waveform output
In Ground (0V) source for the built-in DAC
In Input terminal for keys and switches
Out Key and switch scan signal input
Not used.
In Ground (0V) source for the built-in LED driver
In Keyboard LED drive signal output
AVDD
T2
2SC1740SQ
R12
C9
R30
AG
AG
AG
— 4 —
Function
Power OFF: 0V, Power ON: +5V
R14
R13
C11
AG