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SYSTEM RESPONSE
As soon as DMA starts,
a. Copy to "back-up" length register from AUDOLEN.
b. Copy to "back-up'' location register from AUDOLCL (will be used as a pointer showing
current data word to fetch).
c. Create an interrupt for the 68000 saying that it has completed retrieving working copies
of length and location registers.
d. Start retrieving audio data each allocated DMA time slot.
PLAYING MULTIPLE TONES AT THE SAME TIME
You can play multiple tones either by using several channels independently or by
summing the samples in several data sets, playing the summed data sets through a single
channel.
Since all four audio channels are independently programmable, each channel has its own
data set; thus a different tone or musical note can be played on each channel.
MODULATING SOUND
To provide more complex audio effects, you can use one audio channel to modulate
another. This increases the range and type of effects that can be produced. You can
modulate a channel's frequency or amplitude, or do both types of modulation on a channel
at the same time.
Amplitude modulation affects the volume of the waveform. It is often used to produce
vibrato or tremolo effects. Frequency modulation affects the period of the waveform.
Although the basic waveform itself remains the same, the pitch is increased or decreased
by frequency modulation.
The system uses one channel to modulate another when you attach two channels. The
attach bits in the ADKCON register control how the data from an audio channel is
interpreted (see the Table below). Normally, each channel produces sound when it is
enabled. If the "attach" bit for an audio channel is set, that channel ceases to produce
sound and its data is used to modulate the sound of the next higher-numbered channel.
When a channel is used as a modulator, the words in its data set are no longer treated as
two individual bytes. Instead, they are used as "modulator" words. The data words from
the modulator channel are written into the corresponding registers of the modulated
channel each time the period register of the modulator channel times out.
- Audio Hardware 145 -
Содержание Amiga A1000
Страница 1: ...AMIGA HARDWARE REFERENCE MANUAL 1992 Commodore Business Machines Amiga 1200 PAL...
Страница 20: ...Figure 1 1 Block Diagram for the Amiga Computer Family Introduction 11...
Страница 21: ...12 Introduction...
Страница 72: ...Figure 3 12 A dual Playfield display Playfield Hardware 63...
Страница 87: ...Figure 3 24 Horizontal Scrolling 78 playfield hardware...
Страница 101: ...92 Playfield Hardware...
Страница 199: ...Figure 6 9 DMA time slot allocation 190 Blitter hardware...
Страница 203: ...Figure 6 13 Blitter Block Diagram 194 Blitter Hardware...
Страница 229: ...220 System Control Hardware...
Страница 246: ...Figure 8 8 Chinon Timing diagram cont Interface Hardware 237...
Страница 265: ...256 Interface Hardware...
Страница 289: ...280 Appendix A...
Страница 297: ...288 Appendix B...
Страница 298: ...APPENDIX C CUSTOM CHIP PIN ALLOCATION LIST NOTE Means an active low signal Appendix C 289...
Страница 302: ...APPENDIX D SYSTEM MEMORY MAP Appendix D 293...
Страница 343: ...334 Appendix F...
Страница 351: ...342 Appendix G...
Страница 361: ...352 Appendix H...
Страница 367: ...358 Appendix I...