diff options
Diffstat (limited to 'doc/api-asm.68k')
| -rw-r--r-- | doc/api-asm.68k | 47 |
1 files changed, 42 insertions, 5 deletions
diff --git a/doc/api-asm.68k b/doc/api-asm.68k index b6fa48b..8c0995c 100644 --- a/doc/api-asm.68k +++ b/doc/api-asm.68k @@ -51,11 +51,6 @@ Echo_StopBGM Stops playback of background music. Used both to stop and to pause music (the latter can be undone with Echo_ResumeBGM, see below). -Echo_ResumeBGM - - Resumes playback of whatever background music was playing last time before - Echo_StopBGM was called. Used when you want to unpause music. - ============================================================================= *** Sound effects *** @@ -71,6 +66,28 @@ Echo_StopSFX ============================================================================= +*** Direct events *** + +Echo_PlayDirect + + Injects events to be played as part of the BGM the next tick. The register + a0 points to the ESF data to be injected. + + The injected events are a small stream on their own. The last event must + be $FF (this will return back to the BGM). Do *not* issue $FC, $FD or $FE + events, as you'll just break everything instead. + + The buffer is small, so don't go overboard. There's room for up to 128 + bytes (though again, each event is just 2-3 bytes). If there were direct + events pending to play, the new events will be appended at the end, so + take this into account when it comes to the buffer usage. You can check + if there are pending events with Echo_GetStatus (see bit 14) if you're + worried about running out of space. + + The buffer is only checked every tick. + +============================================================================= + *** Control *** Echo_GetStatus @@ -80,12 +97,32 @@ Echo_GetStatus Bit 0 .... Sound effect is playing Bit 1 .... Background music is playing + Bit 14 ... Echo isn't done parsing direct events Bit 15 ... Echo is busy (can't take commands) The API will automatically wait if you try to send a command while Echo is busy, so the only reason to check for that is if you don't want to halt the 68000 until Echo is ready to take more commands. +Echo_SetVolume + + Sets the global volume. Register d0 is a byte value ranging from 0 + (quietest) to 255 (loudest), and every channel is affected immediately. + The scale of the volume in this case is *linear*. + + Note that since PCM doesn't have volume, it gets toggled on/off depending + on the volume value (the cut off point is at 25%). + +Echo_SetVolumeEx + + Sets the global volume for each channel separately. Register a0 points to + a list of 13 bytes (one for each Echo channel). Values for FM and PSG + channels are given in the same way as in events, that is: logarithmic + scale, 0..127 for FM, 0..15 for PSG, lower = louder. + + The last byte (the one belonging to the PCM channel) is used to toggle + whether PCM plays, either 0 (disabled) or 1 (enabled). + ============================================================================= *** Settings *** |