Table 27 - Communication Functions - Nintendo GAME BOY ADVANCE Programming Manual

May 25, 2005
13 Communication Functions
Game Boy Advance provides the following five communication functions.
1. 8-Bit/32-Bit Normal Communication Function
The use of Game Link cable for the previous DMG/MGB/CGB is prohibited for normal communication.
It is possible to communicate at 256KHz and 2MHz with peripheral equipment that does not use
cables.
Always set the communication speed at 256KHz when performi ng normal communication using a
Game Boy Advance Game Link Cable. Communication cannot be done properly at 2MHz. Also,
please note it will be a one-way communication due to cable connection of multi-play communication.
Due to differences in voltage, communication with DMG/MGB/CGB is not possible. Similarly, commu-
nication with previous DMG/MGB/CGB compatible hardware (pocket printer, etc.) which connects to
an extension connector is not possible.
2. 16-Bit Multi-player Communication Function
This multiple/simultaneous communication function uses UART system to enable communication of up
to 4 Game Boy Advance units.
A special cable for Multi-player communication is necessary.
3. UART Communication Function
Enables high-speed communication by UART system.
4. General-Purpose Communication Function
Enables communication by any protocol through direct control of the communication terminal.
5. JOY Bus Communication Function
Enables communication using Nintendo's standardized Joy bus.
Selecting Communication Function
All the communication functions use an external expansion 6-pin connector. Communication functions are
switched by the communication function set flag of the communication control register RCNT (2-bit) and
the communication mode set flag of the serial communication control register SIOCNT (2-bit), which are
described later.

Table 27 - Communication Functions

Communication
Functions
General-Purpose
JOY Bus
8-Bit Serial
32-Bit Serial
16-Bit Serial
UART
(* ... any)
© 1999-2005 NINTENDO
RCNT
d15 d14
1 0
1 1
0 *
0 *
0 *
0 *
SIOCNT
d13 d12
* *
* *
0 0
0 1
1 0
1 1
AGB-06-0001-002-B13
Released: May 27, 2005
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