Difference between revisions of "Echo"
From Sega Retro
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! Event||Description | ! Event||Description | ||
|- | |- | ||
− | | $ | + | | $10 |
| Note off FM channel #1 | | Note off FM channel #1 | ||
|- | |- | ||
− | | $ | + | | $11 |
| Note off FM channel #2 | | Note off FM channel #2 | ||
|- | |- | ||
− | | $ | + | | $12 |
| Note off FM channel #3 | | Note off FM channel #3 | ||
|- | |- | ||
− | | $ | + | | $14 |
| Note off FM channel #4 | | Note off FM channel #4 | ||
|- | |- | ||
− | | $ | + | | $15 |
| Note off FM channel #5 | | Note off FM channel #5 | ||
|- | |- | ||
− | | $ | + | | $16 |
| Note off FM channel #6 | | Note off FM channel #6 | ||
|- | |- | ||
− | | $ | + | | $18 |
| Note off PSG channel #1 | | Note off PSG channel #1 | ||
|- | |- | ||
− | | $ | + | | $19 |
| Note off PSG channel #2 | | Note off PSG channel #2 | ||
|- | |- | ||
− | | $ | + | | $1A |
| Note off PSG channel #3 | | Note off PSG channel #3 | ||
|- | |- | ||
− | | $ | + | | $1B |
| Note off PSG channel #4 | | Note off PSG channel #4 | ||
|- | |- | ||
− | | $ | + | | $1C |
| Note off PCM channel | | Note off PCM channel | ||
|} | |} | ||
+ | These events do a "note off" at the specified channel. | ||
+ | |||
+ | ''' $1C: Note off PCM channel ''': | ||
+ | |||
+ | This event does a "note off" at the PCM channel. This means that any PCM playback is immediately stopped. FM channel #6 is immediately enabled as well. | ||
== Links / Download == | == Links / Download == | ||
[http://github.net/sikthehedgehog/echo GitHub repository for Echo], including docs, source, binaries, etc. | [http://github.net/sikthehedgehog/echo GitHub repository for Echo], including docs, source, binaries, etc. |
Revision as of 04:05, 17 November 2011
Echo is a new sound-engine for the Sega Mega Drive created by Sik. It's Z80-based and allows full control over the sound hardware. Its purpose is to provide a free, open-source possibility to implement music and sound effects in programs, demos or games developed for the system. It is currently in beta state, albeit functional for the most part.
Event list
Note on
Event | Description |
---|---|
$00nn | Note on FM channel #1 |
$01nn | Note on FM channel #2 |
$02nn | Note on FM channel #3 |
$04nn | Note on FM channel #4 |
$05nn | Note on FM channel #5 |
$06nn | Note on FM channel #6 |
$08nn | Note on PSG channel #1 |
$09nn | Note on PSG channel #2 |
$0Ann | Note on PSG channel #3 |
$0Bnn | Note on PSG channel #4 |
$0Cnn | Note on PCM channel |
For $00 to $06 :
These events do a "note on" at the specified FM channel. The event is followed by a byte, which indicates which note to play. The value is as follows, where "octave" ranges from 0 to 7 and "semitone" ranges from 0 to 11:
32 * octave + 2 * semitone + 1
For $08 to $0A :
These events do a "note on" at the specified square wave PSG channel. The event is followed by a byte, which indicates which note to play. The value is as follows, where "octave" ranges from 0 to 5 and "semitone" ranges from 0 to 11:
24 * octave + 2 * semitone
$0Bnn: Note on PSG channel #4 :
This event does a "note on" at the noise PSG channel. The event is followed by a byte, which indicates what kind of noise to play. The following values are valid:
$00 ... Periodic noise, high pitch $01 ... Periodic noise, medium pitch $02 ... Periodic noise, low pitch $03 ... Periodic noise, PSG3 frequency $04 ... White noise, high pitch $05 ... White noise, medium pitch $06 ... White noise, low pitch $07 ... White noise, PSG3 frequency
When using values $03 and $07, the third square wave PSG channel controls the noise frequency. You can change this frequency using the events to change the frequency of that channel (usually you'd use event type $3A).
$0Cnn: Note on PCM channel :
This event does a "note on" at the PCM channel. More specifically, it starts playback of a PCM sample. This event is followed by a byte, that specifies an index in the pointer list indicating where's the sample data. Samples are stored as EWF (Echo Waveform Format).
NOTE: FM channel #6 will be disabled. That channel will be re-enabled when PCM playback is over (either because the waveform is over or because the channel is stopped explicitly).
Note off
Event | Description |
---|---|
$10 | Note off FM channel #1 |
$11 | Note off FM channel #2 |
$12 | Note off FM channel #3 |
$14 | Note off FM channel #4 |
$15 | Note off FM channel #5 |
$16 | Note off FM channel #6 |
$18 | Note off PSG channel #1 |
$19 | Note off PSG channel #2 |
$1A | Note off PSG channel #3 |
$1B | Note off PSG channel #4 |
$1C | Note off PCM channel |
These events do a "note off" at the specified channel.
$1C: Note off PCM channel :
This event does a "note off" at the PCM channel. This means that any PCM playback is immediately stopped. FM channel #6 is immediately enabled as well.
Links / Download
GitHub repository for Echo, including docs, source, binaries, etc.