General Purpose Communication - Nintendo 1504166 - Game Boy Advance SP Edition Console Programming Manual

AGB Programming Manual

13.4 General Purpose Communication

By setting (d15, d14 )= (1, 0) for RCNT register, it will change to a general purpose
communication mode.
In this mode, all of the terminals SI, SO, SC, and SD become pull-up and operate as
general purpose input/output terminals. Each of the communication terminals SI, SO,
SC, and SD can be directly controlled.
Address Register
134h RCNT
Communication Function Set Flag
10: General Purpose Input/Output Terminal
11: JOY Bus Communication
RCNT [d15 - d14] Communication Function Set Flag
When set to 00 or 01, operates as a serial communication(8-bit/16-bit
serial communication, multi-player communication, UART communication
function) terminal.
When set to 10, can be used as a general purpose input/output terminal.
When set to 11, can be used as a JOY Bus communication terminal.
RCNT [d08] Interrupt Request Enable Flag
When general purpose input/output is set(R[d15,d14]=[1,0]) with the
communication function set flag, a 1 causes an interrupt request to be
generated with the falling of the SI Terminal(edge detect).
When set to 0, no interrupt request is generated.
RCNT[d07 - d04] Input/Output Selection Flag
When general purpose input/output is set (R[d15,d14]=[1,0]) with the
communication function set flag, a setting of 0 allows the corresponding
terminal to be used as an input terminal. A setting of 1 allows the
corresponding terminal to be used as an output terminal.
[Caution]
Always set the SI terminal to an input. If it is set to an output, a problem
may occur with some connecting equipment.
©1999 - 2001 Nintendo of America Inc.
15 14 13 12 11 10 09 08 07 06 05 04 03 02 01 00
0*: Serial Communication
SO SI SD SC
Input/Output Selection Flag
0: Set to Input
1: Set to Output
Interrupt Request Enable Flag
0: Disable
1: Enable
148
Communication Functions
Attributes
R/W 0000h
SO SI SD SC
Data Bit
D.C.N. AGB-06-0001-002B4
Initial
Value