AGB Programming Manual
Communication Functions
©1999 - 2001 Nintendo of America Inc.
142
D.C.N. AGB-06-0001-002B4
13.3 UART Communication Functions
UART communications can be illustrated using the following drawing.
SI
SO
SD
SC
SI
SO
SD
SC
In UART communication mode, a HI level is output from the SD terminal.
When the receive data register (or the receive FIFO) is full, a HI is output from the SD
terminal. When it is not full, a LO is output from the SD terminal if the receive enable
flag is set. A HI is output if it is reset.
The output of the SD terminal of the other machine is input to the SC terminal.
Once data is written to the send data register, data is sent after a “Start bit” (1 bit) is
sent from the SO terminal. However, when the CTS flag for the Control Register is
set, data can be sent only when there is a LO input to the SC terminal. The Stop bit is
a fixed 1 bit.
Data Register
15 14
13
12 11
10
09 08
07
06
05 04
03
02 01
00
SIO
DATA8
12Ah
0000h
R/W
Address
Register
Attributes
Initial
Value
Relations Between Data Register, FIFO, and Shift Register
When sending or receiving, there are 4 bytes of FIFO. By using the FIFO enable flag
for the control register SIOCNT, you can select whether to use or not use FIFO.
When FIFO is not Used
If written to a data register SIODATA8, data is written to a send shift register, and if
read, data is read from a receive shift register. (Only the lower 8 bits are valid.)