Yamaha Vintage DX7 Special Edition ROM Instrukcja serwisowa - Strona 9
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9.
LCD
Data from the main CPU is decoded and displayed at the LCD unit.
10.
EGS (Envelope Generator)
8 bits of data are received from the main CPU, and envelope and frequency data are
sent to OPS.
11.
OPS (Operator)
The OPS uses a sine table to generate waveform data to be sent to the DAC from the
received envelope and frequency data.
The OPS permits combining the 6 operators in 32 different combinations. The combina-
tions are called "algorithms". One of the 6 operators is able to feed the sine table output
back to the input. The feedback level and algorithm data is received from the main
CPU.
12.
DAC
A BA9221 DAC is used. The DAC converts the digital waveform data from the OPS to an
actual analog waveform. The amplitude scale factor of the analog waveform is controlled
via SF0 ~ SF3. This signal is then fed to the sample & hold and low-pass filter circuits
from which it is sent to the output terminal. A reference voltage is applied to pin 14 of the
DAC. 8 reference voltages are generated by the muPD405 1, and the total level is exter-
nally controlled.
13.
MIDI (Musical Instrument Digital Interface)
Permits data transfer with other devices. Data is received by P3 of the main CPU via a
photo-coupler, and data is output from main CPU pin P24.
1
EGS Functions
Receives data from the CPU, generates envelope & frequency data, & transmits the gener-
ated data to OPS.
(see EGS block diagram)
Data received from the CPU is latched in the EGS & sent to the internal data buss.
2
EGS Rate/Level Buffer
Rate refers to the time required for the next level to be reached. For example, Rl is the time
EGS