Nintendo 1504166 - Game Boy Advance SP Edition Console Programming Manual page 143

AGB Programming Manual
When FIFO is Used
If written to a data register SIODATA8, data is written to a send FIFO. If all the
contents of the send shift register are shifted out, data is transferred from a send FIFO
to a shift register, immediately.
Please note when using this operation, that data is immediately transferred to a shift
register when the first data is written to the data register, and the interrupt request
condition is met as a send FIFO becomes empty. Also, when read, data is read from
a receive FIFO. (Only the lower 8 bits are valid.)
Example: Writing Data Registers
©1999 - 2001 Nintendo of America Inc.
143
Communication Functions
D.C.N. AGB-06-0001-002B4