RegistersEdit

Old3DS Name Address Width Used by
Yes I2S1_CNT 0x10145000 2 Codec sysmodule, AgbBg, TwlBg
Yes I2S2_CNT 0x10145002 2 Codec sysmodule, AgbBg, TwlBg


I2S1_CNTEdit

Bit Description
0-5 DSP volume (doesn't affect csnd).
6-11 GBA hardware master volume. And DSi too?
12 Unknown purpose. Maybe direction for microphone input?
13 I2S frequency. 0=32.728498046875 kHz, 1=47.605088068181818181818 kHz.
14 First MCLK output. 0=8.3784955 MHz, 1=16.756991 MHz.
15 Enable (0=Disabled, 1=Enabled)

This I2S line is used the DSP, GBA hardware and microphone.

This is usually set to 0xC800 or 0xC820 when the DSP is active.


I2S2_CNTEdit

Bit Description
0-12 Unused (0).
13 I2S frequency. 0=32.728498046875 kHz, 1=47.605088068181818181818 kHz.
14 Second MCLK output. Connected to the CODEC chip. 0=8.3784955 MHz, 1=16.756991 MHz.
15 Enable (0=Disabled, 1=Enabled)

This I2S line is used by CSND.

Usually set to 0xE000.