This page describes the structure of the CSND shared memory.

Value=1 begins audio playback. Value=0 stops audio playback, and also seems to reset the audio channel CSND registers so that those registers need re-initialized before audio can be played from this channel again.

This command starts playing the audio channel with value=1. Once the audio channel is playing, value=0 pauses the audio channel playback, and value=1 resumes the audio channel playback. Value=1 has no affect when the audio channel is already playing, likewise for value=0 when the audio channel is not playing.

This sets the encoding field in the CSND channel CNT register(that field is cleared to zero first), command 0xE also sets this field.

This sets the address and size of the second block of an audio channel. The CSND module writes these fields to the channel register for the physical address of the second block and the register for the block size.

This is the same as cmd2 except for the looping field. CSND will only write to this channel CNT register for updating the looping field if bit15 in the channel CNT register is value zero.

When value=0, CSND module will clear bit7 in the channel CNT register. Otherwise, CSND module sets bit7 in the channel CNT register.

This is the same as cmd5, except this updates channel CNT bit6 instead. CSND module will only update CNT here if bit15=0 in CNT.

This command updates bit0 through (at least) bit2 of the channel’s CNT register. These bits control the duty of a PSG square wave:

 0  12.5% "_______-_______-_______-"
 1  25.0% "______--______--______--"
 2  37.5% "_____---_____---_____---"
 3  50.0% "____----____----____----"
 4  62.5% "___-----___-----___-----"
 5  75.0% "__------__------__------"
 6  87.5% "_-------_-------_-------"
 7   0.0% "________________________"

This sets the sample rate. This value is written to the channel CNT high-u16, which command 0xE also writes to. This command is used immediately after command 0xE.

This sets the playback and capture volumes for the specified channel. This command is usually used after command 0x8(user processes use cmd8 a second time before using this command).

This sets the address and size of the first block of an audio channel. The CSND module writes these fields to the channel register for the physical address of the first block and the register for the block size.

This command is used for setting the IMA-ADPCM state used to play the first block (when IMA-ADPCM encoding is used), prior to using command 0xE. CSND channelslotregister+0x18 = (u16)cmdword[3] | ((cmdword[4] & 0xFF)<<16). CSND channelslotregister+0x1C = 0.

This is used for setting the IMA-ADPCM state used to play the second block (when IMA-ADPCM encoding is used). channelslotregister+0x1C = (1<<31) | (u16)cmdword[3] | ((cmdword[4] & 0xFF)<<16).

This command configures bit31 of channelslotregister+0x1C. This bit indicates whether the hardware will load ADPCM state from said register everytime the second block is to be played; or if it will continue using the same state used for the previously emitted sample.

This initializes the CSND channel registers located at: 0x1EC03400 + (channel_index*0x20). It is unknown if stereo samples are supported. In manual mode, the hardware plays the audio data of the first block endlessly ignoring the size field. In one-shot mode, the hardware plays the first block with the specified size and then stops. When looping is enabled, the hardware plays the first block once and then repeats the second forever. Before playing a block, the hardware reads the corresponding address register in order to know where it is located. The block size is either read only once at the beginning (mode 3) or before each block (mode 1, normal looping).

Bits 0 through 5 are written as zero to the CNT register.

PSG: Channels 8 through 13 play a square tone that is 32 samples long. Channels 14 and 15 play noise. The duty of the square tones is set using command 0x7.

This channel is similar to command 0xE, but it is tailored for configuring PSG Tone channels (8, 9, 10, 11, 12, 13) as it contains a duty parameter. Channel format is set to PSG.

This channel is identical to command 0xF except for not having a duty parameter. Presumably used to configure PSG Noise channels (14, 15).

Writes bit15 of (u16*)(0x1EC03800+16*X).

Writes bit0 of (u16*)(0x1EC03800+16*X).

Writes bit1 of (u16*)(0x1EC03800+16*X).

Writes bit2 of (u16*)(0x1EC03800+16*X).

Sets (u16*)(0x1EC03800+16*X+4) = -Y.

Sets (u32*)(0x1EC03800+16*X+8) = Y, and (u32*)(0x1EC03800+16*X+12) = Z.

Does the same thing as all 0x100-0x106 combined.

Sends some interrupt to the DSP?

CSND module writes state info(including state from CSND registers) for each audio channel to shared-memory for this command.

This section describes the structure of the data located at offset1(from CSND:Initialize) in shared-memory. This data is updated by command 0x300, and by commands which update the channel physical address registers. The following describes the format of the entries located here.