Figure 107 - The Siocnt Register (16-Bit) - Nintendo GAME BOY ADVANCE Programming Manual

May 25, 2005
13.2.4 Control Register
If you set Register SIOCNT (d13,d12) = (1,0) when Register RCNT (d15) = (0), you will go to 16-bit multi-
player communication mode.
15 14 13 12 11 10 09 08 07 06 05 04 03 02 01 00
Address Register
128h SIOCNT
SIOCNT [d14] Interrupt Request Enable Flag
When set to 0, no interrupt request is generated.
When set to 1, an interrupt request is generated upon the completion of multi-player communication.
SIOCNT [d07] Start Bit/Busy Flag
1. Master (d02 is 0)
When set to 0, no data is transferred.
When set to 1, a data transfer is started. Upon completion of the data transfer, it is automatically reset.
Caution
Due to individual differences in Game Boy Advance hardware, there is a variation in the timing of inter-
rupt occurrences. Always use a timer when sending data, so that you have an adequate interval
between communications (minimum send interval + 600 clocks). 600 clocks is the guaranteed value
that considers the variation in timing of interrupt occurrence. Refer to Game Boy Advance Program-
ming Cautions 5.1."16-Bit MultiPlayer Communications."
2. Slave (d02 is 1)
Set during input of transmit start bit (LO source oscillation cycle × 3 (approximately 180ns)), and reset
when the transfer is complete.
© 1999-2005 NINTENDO
16-Bit Multi-player Communication

Figure 107 - The SIOCNT Register (16-Bit)

1 0
Interrupt Request Enable Flag
0: Disable
1: Enable
Baud Rate
00: 9600bps
01: 38400bps
10: 57600bps
11: 115200bps
SI Terminal
SD Terminal
Multi-player ID Flag
00: Master
01: 1st Slave
10: 2nd Slave
11: 3rd Slave
Communication Error Flag
0: Normal
1: Error
(Master) Start Bit/ (Slave) Busy Flag
0: No transfer 0: Free
1: Start transfer 1: Busy
Released: May 27, 2005
117
Attributes Initial Value
R/W 0000h
AGB-06-0001-002-B13