Figure 101 - Multi-Player Communication Connection Status - Nintendo GAME BOY ADVANCE Programming Manual

May 25, 2005
13.2 16-Bit Multi-player Communication
Game Boy Advance enables multi-player communication between up to 4 units using a special cable.
Depending on the connection status, 1 unit is established as the master and transfers data to slaves in
order, one after another.
13.2.1 Connection Status during Multi-player Communication

Figure 101 - Multi-Player Communication Connection Status

Master
SI
SO
SD
SC
In multi-player communication mode the SC and SD become pull-up input terminals. Immediately following
a reset or in another communication mode, LO is output from the SD terminal. Once the SD terminal
becomes HI, you can tell that all connected terminals have entered multi-player communication mode.
The SI terminal is in pull-up input, but due to the multi player Game Boy Advance Game Link cable it
becomes pull-down. Thus, once all of the terminals are in multi-player mode, the terminal that is LO input
to the SI terminal becomes the master. The terminal that is HI input to the SI terminal becomes the slave.
If you set the start bit of Register SIOCNT of the master, the data registers SIOMULTI0, SIOMULTI1,
SIOMULTI2, and SIOMULTI3 of the master are initialized to FFFFh.
Additionally, the "SYNC signal" (LO level) is output from the SC terminal. At the same time, the "Start bit"
(LO level) is output from the SD terminal. Next, the data from Register SIOMLT_SEND is output and a
""Stop bit" (HI level) is output.
After this is done, the master makes the SD terminal become pull-up input, and LO is output from the SO
terminal.
Each slave detects the "SYNC Signal" output from the master and initializes all of the data registers
(SIOMULTI0, SIOMULTI1, SIOMULTI2, and SIOMULTI3) to FFFFh. The data output from the master is
stored in the master and each slave's SIOMULTI0 register.
If LO is input to the SI terminal of the slave which was connected immediately f ollowing the master, a "Start
bit" (LO level) is output from the SD terminal. Next, data from Register SIOMLT_SEND is output, and lastly
a "Stop bit" (HI level) is output.
After this, the SD terminal goes to pull-up input and LO is output from the SO terminal.
At this point, the data output from the first slave is stored in the master and each slave's SIOMULTI1 Reg-
ister.
In this way, each slave is sent and all transmissions are carried out.
In the following situations the master produces a "SYNC Signal" (pull-up input after the output of a 5 cycle
HI interval of source oscillation) and the transmission ends:
• After the master outputs its own "Stop bit", the next "Start bit" is not input after a certain period of time.
• After a "Stop bit" is received from the first or second slave, a "Start bit" is not input after a certain period
of time.
• A "Stop bit" is received from the third slave.
© 1999-2005 NINTENDO
16-Bit Multi-player Communication
First Slave Second Slave
SI
SO
SD
SC
Third Slave
SI SI
SO SO
SD SD
SC SC
AGB-06-0001-002-B13
Released: May 27, 2005
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