. CIRCUIT EXPLANATION
1. KLM-6028 (CPU SECTION)
In DDD 5, a 1 chip microprocessor pPD 78C10 controls each operation and CPU is operated by means of a 12 MHz ceramic oscillator.
PORT A outputs the scan code of the key matrix and data of LCD and LED.
PORT B is used for display (LCD and LED) control, muting of output sound, output of read/ write signals of the IC card, etc.
PORT C is used for interfacing of the external I/ 0, etc.
2. GATE ARRAY (MB64HD117)
This gate array latches the multiplexed address/ data and outputs it as the address lower 8 bits. It also takes in the address higher 8 bits and outputs chip select signals of peripheral ICs (memory, gate array for sound source, etc.) as a data bus buffer.
In addition, it is provided with two I/0 ports; one of them is used for input/output of IC data and the other one is used for input of the key matrix data.
IC9 (27C512) is a programmed ROM with 64 bytes.
Each of IC10 and 11 (pPD4364 CX-15L) is RAM with 8K bytes and composes a RAM area with 16K bytes. This RAM is supported by a lithium battery (BATT 1) when the supply of the power stops.
MIDI OUT outputs CPU TXD (PCO) by
buffering it at DT1 and DT2 (BA1A4M).
MIDI IN is isolated by a photo-coupler PC1
(PC900) and inputted into CPU RXD (PC-1).
5. FOOT switch (TAP, START/STOP, INTRO/FILL)
TAP The tap tempo is inputted
into CPU INT2 (PC3).
OS START/STOP The START / S'I'OP is buffer-
ed by IC16 (FIC14) and activates Ql 1 (2SC 2185) of the key matrix.
Q< INTRO/FILL The INTRO / F1LL is buffer-
ed by IC16 (HC14) and activated @10 (2SC 2785) of the key matrix.
6. TAPE OUT
TAPE OUT is buffered and outputted at Q15 (2SC 2785) using PC4 and PCl of CPU.
7. TAPE IN
The wave of signal inputted through TAPE IN jack is formed by IC20 (4558S) circuit after the level is set by TAPE LEVEL SW.
8. RESET CIRCUIT
'I'he reset signal is produced by IC15 (RESK'I' IC: M51951B) and, after the wave is formed by IC16 (HC14), inputted into CPU, GATE ARRAY, RAM, ect.
2. KLM-6028(INST KEY DYNAMICS
The inst key dynamics circuit, consisting of resistance, capacitor, doubled diode, and NOR gate, takes in the ON/OFF data of double-contact switch sent from the inst key substrate (KLM-6031) and produces the dynamics data based upon its time lag.
Each one circuit is connected to every 7 inst keys and the data, which are selected by 1C3 (4051) out of 7 dynamics data, are sent to CPU through IC2 (072D). Each key activates any of @2-Q8 (2SC 2785) of the key matrix.
3. KLM-6028 (SOUND SOURCE GATE
1. Sound source gate array (MB661107)
this gate array is connected to CPU and, under observation by CPU, controls the sound source data in the voice ROM and the ROM card (decay, out level, panning, and mono/poly/exclusive).