Casio CTK-220L Service Manual page 6

CPU (LSI1: MSM6755B-13)
The CPU contains a sound data ROM and a DAC (Digital to Analog Convertor), and it provides a sound
waveform in accordance with the pressed key and the selected tone. The CPU also controls key input, button
input and LED driving. The following table shows the pin functions of LSI1.
Pin No. Terminal
1
2 MWEB
3 ~ 5
6
7 ~ 19 MA1 ~ MA11
20 ~ 27 MD0 ~ MD7
28, 29 NC1, NC2
30
31
32, 33 XTLO, XTLI
34
35
36 P24/RXD
37 P25/TXD
38
39
40
41
42, 43 NC5, NC6
44
45
46
47
48
49
50
51
52
53
54
55, 56 MOD1, MOD2
57
58 ~ 65 KI0/P30 ~ KI7/P37
66 ~ 73 KO0/P50 ~ KO7/P57
74 ~ 77 KO8/P20 ~ KO11/P23
78
79
80 ~ 95 LX0 ~ LX7, LY0 ~ LY7
96
97 ~ 100 MA18 ~ MA15
In/Out
MA14 —
Out
— —
MA0 Out
—
Out
—
DGND In
DVCC In
In/Out
NC3 —
RSTB In
—
—
NMI In
APO Out
NC4 —
REFH Out
—
DAOR Out
NC7 —
AVdac In
DAOL Out
REFL Out
AGdac In
AGadc In
ANI —
AVadc In
NC8 —
MOD0 In
In
P40 In
In
Out
Out
NC9 —
LVCC In
Out
LGND In
—
Not used.
Clock for LED latches
Not used.
7-seg. LED drive signal
Not used.
7-seg. LED drive signal
Not used.
Ground (0 V) source
+5 V source
20 MHz clock input/output
Not used.
Reset signal input
Not used. Connected to +5 V.
Not used.
Power ON signal input. Connected to +5 V.
APO (Auto Power Off) signal output
Not used.
Terminal for the internal DAC
Not used.
Right channel sound waveform output
Not used.
+5 V source for the internal DAC and ADC
Left channel sound waveform output
Terminal for the internal DAC and ADC
Ground source for the internal DAC
Ground source for the internal ADC
Not used. Connected to ground.
+5 V source for the internal ADC
Not used.
Mode selection terminal. Connected to +5 V.
Mode selection terminal. Connected to ground.
APO cancellation signal
Terminals for key/button input signal
Terminals for key scan signal
Terminals for button input signal
Not used.
+5 V source
LED drive signal
Ground source
Not used.
— 4 —
Function