Nintendo 1504166 - Game Boy Advance SP Edition Console Programming Manual page 86

AGB Programming Manual
With the preceding preparations, direct sound is executed as follows.
Direct Sound Execution
1. When the specified timer overflows due to a count up, the audio data are passed
from the FIFO to the sound circuit.
2. If 4 words of data remain in the FIFO as the transfer count progresses, the FIFOs
for direct sounds A and B output a data transfer request to the specified DMA
channel.
3. If the DMA channel receiving the request is in sound FIFO transfer mode, 4 words
of data are provided to the sound FIFO (the DMA WORD COUNT is ignored).
The preceding is repeated starting from 1.
©1999 - 2001 Nintendo of America Inc.
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Sound
D.C.N. AGB-06-0001-002B4