Casio Oriental Maestro AT1, Service Manual

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CPU (HD6433298A36P)
The 16-bit CPU contains a 32k-bit ROM, a 1k-bit RAM, seven 8-bit I/O ports, an A/D convertor and serial
interfaces. The CPU accesses to the working strage RAM, the DSP and the key touch LSI. The CPU also
controls buttons, bender input, LEDs and MIDI input/output.
The following table shows the pin functions of the CPU.
Digital Signal Processor (HG51B155FD)
Upon receipt of note numbers and their velocities, the DSP reads sound and velocity data from the sound
source ROM in accordance with the selected tone; the DSP can read rhythm data simultaneously when a
rhythm pattern is selected. Then it provides 16-bit serial signals containing data of the melody, chord,
bass, and percussion to the DAC. The DSP also adds the selected effect to the sound data using a 64k-bit
RAM.
The following table shows the pin functions of the DSP.
Pin No. Terminal In/Out Function
1 P40 Out KO signal data output
2 P41 Out Clock for KO signal data
3 P42 Out APO (Auto Power Off) signal output. ON: High OFF: Low
4 P43 Out Read enable signal output
5 P44 Out Write enable signal output
6 P45 Not used
7 P46 Out 10 MHz clock output
8 P47 In Wait signal input. Connected to +5 V.
9 TXD Out MIDI signal output
10 RXD In MIDI signal input
11 P52 Out Reset signal output
12 -RESET In Reset signal input
13 -NMI In Power ON signal input
14 VCC In +5 V source
15 -STBY In Standby signal input. Connected to +5 V.
16 VSS In Ground (0 V) source
17, 18 XTAL,EXTAL In 20 MHz clock input
19, 20 MD1, MD0 In Mode selection input.(Internal ROM mode --- MD1: High MD0: Low)
21 AVSS In Ground (0 V) source for the built-in DAC
22 AN0 In Analog input. Connected to ground.
23 ~ 29 P71 ~ P77 In Ternimal for button input signal
30 AVCC In +5 V source for the built-in DAC
31 ~ 38 P60 ~ P67 Out LED segment signal output
39 VCC In +5 V source
40 P27 Not used
41 ~ 56 P26 ~ P10 Out Address bus
48 VSS In Ground (0 V) source
57 ~ 64 P30 ~ P37 In/Out Data bus