SCSP was developed with multimedia support in mind, so its audio features are even more sophisticated and sound quality than ever before. The calculation section also has performance comparable to that of commercially available synthesizers, and can produce a large number of notes. In addition, various interfaces are provided in consideration of future extensibility. The DSP section can also create multiple sound fields, making it effective for various sound field reproductions and special effects such as 3D sound localization.
The characteristics of LSI are described below.
●Sampling frequency
Sound source resampling frequency (constant playback rate) 44.1KHz
Waveform data sampling frequency 0 (CD) ~ 44.1KHz
●Features
Equipped with 32 slots for both FM and PCM.
Equipped with a total of 32 LFOs, one for each slot (completely independent).
Equipped with 32 4-segment EGs.
It has two built-in CPU interfaces: a sound CPU and a main CPU.
It has a built-in MIDI interface.
Equipped with 128 step DSP.
It has a built-in input mixer to select DSP input.
It has a built-in output mixer that mixes the sound source output and DSP output.
Equipped with a new FM calculation method.
■2.2 LSI specifications
Detailed specifications of the sound CPU (MC68EC000) and SCSP are described below.
●Sound CPU specifications
SOUND CPU MC 68EC000-12 12.5MHz version
Operating frequency
11.2896MHz
CPU instructions
Fully compatible instruction system with MC68000CPU Note 1
interrupt signal
Level 1-7 interrupts with auto-vectoring
Hardware configuration
Configuration in which the MC6800 (8-bit) interface is removed from the MC68000CPU
Speech synthesis method
PCM voice synthesis and FM voice synthesis method noise sound source (can be used together)
FM voice synthesis can use not only the conventional 4 operator (slot) type but also 2 to 32 operators to perform any FM connection. You can also configure feedback settings as you like.
Sound source resampling frequency
44.1KHz fixed, linear interpolation
Waveform data format
16-bit linear and 8-bit linear 2'S complement method
Number of audio processing slots (Number installed: 32)
Equivalent to 1 operator (1 slot) for PCM sound source and FM sound source
Maximum (maximum) number of simultaneous polyphony (number installed: 1 to 32)
All 4 operator (slot) type FM sounds will have 8 sounds, and all PCM sounds will have 32 sounds. The number of slots used for one FM sound can be set arbitrarily. Mixed use of FM sound and PCM sound is also possible. Any combination is fine as long as the total number of slots used does not exceed 32.
Waveform loop function
Select from normal, reverse, or alternative loop for each slot
EG (Number installed: 32)
4-segment AMPLITUDE-EG (one unit installed in each slot)
LFO (Number of installed: 32)
One unit installed in each slot (for amplitude/frequency modulation)
Types of LFO output waveforms (number of installed: 4)
4 waveforms: sawtooth, square, triangle, and white noise
Sound source oscillation frequency
-8 to +7 octaves 1024 steps (non-linear) can be set between octaves
◆DSP section for effects
DSP processing speed
128 steps/Fs (multi-parallel processing type DSP Fs=44.1KHz)
Program RAM (capacity: 128W)
128 words x 60 bits
Coefficient data RAM (capacity: 64W)
64 words x 13 bits
Temporary (general purpose) RAM (capacity: 128W)
128 words x 24 bits
This is an interface to connect the system controller (SCU).
●DMA transfer interface
A DMA controller with built-in SCSP enables data transfer between SCSP and sound memory.
●MIDI interface
A serial interface compatible with MIDI standards. However, some external circuitry is required to make it compatible with MIDI connectors.
●External input (external digital audio input interface)
This is an interface that inputs digital audio signals from external equipment (external devices).
●LFO (Low Frequency Oscillator)
A function generator that generates waveforms with frequencies lower than the range that the human ear can hear, and is used as waveforms for various modulations.
●Phase generator
This block calculates and calculates frequency information according to the sound frequency setting of PCM data.
●Address pointer
Generates waveform address values based on phase information etc. from the phase generator.
●Memory controller
This block controls the sound memory by outputting the address generated by the address pointer to the memory and reading data.
●Interpolator
This block performs interpolation calculations on waveform data.
●Envelope Generator (EG: Envelope Generator)
This is a functional calculation block that temporally controls the audio output level.
●Level calculation section
This block calculates the waveform output level based on the level coefficients generated by EG, TL (Total Level), and ALFO.
●DSP
This is an audio DSP that handles SCSP's acoustic special effects.
●Output mixer
This is the final block that has various localization calculation functions and level adjustment functions to combine each audio output into a stereo output.
