Casio CTK-520L Service Manual page 7

CPU (LSI1: MSM6755B-07)
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 built-in DACs. The CPU
also controls key input, button input and LED driving. The following table shows the pin functions of LSI1.
Pin No. Terminal
1 MA14
2 MWEB
3 NCO
4 ~ 19 MA0 ~ MA13
13 MRDB
17 MCSB
20 ~ 27 MD0 ~ MD7
28, 29 NC1, NC2
30 DGND
31 DVCC
32, 33 XTLO, XTLI
34 NC3
35 RSTB
36 P24/RXD
37 P25/TXD
38 NMI
39 APO
40 NC4
41 REFH
42, 43 NC5, NC6
44 DAOR
45 NC7
46 AVdac
47 DAOL
48 REFL
49 AGdac
50 AGadc
51
52 AVadc
53 NC8
54 MOD0
55, 56 MOD1, MOD2
57 P40
58 ~ 65 KI0/P30 ~ KI7/P37
66 ~ 73 KO0/P50 ~ KO7/P57
74 ~ 77 KO8/P20 ~ KO11/P23
78 NC9
79 LVCC
80 ~ 95 LX0 ~ LX7, LY0 ~ LY7
96 LGND
97, 98 MA18, MA17
99, 100 MA16, MA15
In/Out
Out
Out
—
Out
Out
—
In/Out
—
In
In
In/Out
—
In
—
—
In
Out
—
Out
—
Out
—
In
Out
Out
In
In
ANI —
In
—
In
In
In
In
Out
Out
—
In
Out
In
—
Out
Function
Address bus
Clock for LED latches
Not used.
Address bus
Read enable signal
Not used.
Data bus
Not used.
Ground (0 V) source
+5 V source
20 MHz clock input/output
Not used. Connected to ground.
Reset signal input
Not used. Connected to +5 V.
Not used.
Power ON signal input
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.
Address bus
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