Casio CTK-220L manual CPU LSI1 MSM6755B-13

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	In/Out	Function
1	MA14	—	Not used.
2	MWEB	Out	Clock for LED latches
3 ~ 5	—	—	Not used.
6	MA0	Out	7-seg. LED drive signal
7 ~ 19	MA1 ~ MA11	—	Not used.
20 ~ 27	MD0 ~ MD7	Out	7-seg. LED drive signal
28, 29	NC1, NC2	—	Not used.
30	DGND	In	Ground (0 V) source
31	DVCC	In	+5 V source
32, 33	XTLO, XTLI	In/Out	20 MHz clock input/output
34	NC3	—	Not used.
35	RSTB	In	Reset signal input
36	P24/RXD	—	Not used. Connected to +5 V.
37	P25/TXD	—	Not used.
38	NMI	In	Power ON signal input. Connected to +5 V.
39	APO	Out	APO (Auto Power Off) signal output
40	NC4	—	Not used.
41	REFH	Out	Terminal for the internal DAC
42, 43	NC5, NC6	—	Not used.
44	DAOR	Out	Right channel sound waveform output
45	NC7	—	Not used.
46	AVdac	In	+5 V source for the internal DAC and ADC
47	DAOL	Out	Left channel sound waveform output
48	REFL	Out	Terminal for the internal DAC and ADC
49	AGdac	In	Ground source for the internal DAC
50	AGadc	In	Ground source for the internal ADC
51	ANI	—	Not used. Connected to ground.
52	AVadc	In	+5 V source for the internal ADC
53	NC8	—	Not used.
54	MOD0	In	Mode selection terminal. Connected to +5 V.
55, 56	MOD1, MOD2	In	Mode selection terminal. Connected to ground.
57	P40	In	APO cancellation signal
58 ~ 65	KI0/P30 ~ KI7/P37	In	Terminals for key/button input signal
66 ~ 73	KO0/P50 ~ KO7/P57	Out	Terminals for key scan signal
74 ~ 77	KO8/P20 ~ KO11/P23	Out	Terminals for button input signal
78	NC9	—	Not used.
79	LVCC	In	+5 V source
80 ~ 95	LX0 ~ LX7, LY0 ~ LY7	Out	LED drive signal
96	LGND	In	Ground source
97 ~ 100	MA18 ~ MA15	—	Not used.

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