16-Bit Multi-Player Communication - Nintendo 1504166 - Game Boy Advance SP Edition Console Programming Manual

AGB Programming Manual

13.2 16-Bit Multi-player Communication

AGB 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.
Connection Status during Multi-player Communication
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 AGB 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
following 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.
©1999 - 2001 Nintendo of America Inc.
First Slave Second Slave
SI
SO
SD
SC
134
Communication Functions
Third Slave
SI SI
SO SO
SD SD
SC SC
D.C.N. AGB-06-0001-002B4