Nintendo 1504166 - Game Boy Advance SP Edition Console Programming Manual page 146

AGB Programming Manual
SIOCNT [d06] Error Flag
By referring to this error flag, the status of communication errors can be
determined.
When it is 0, no errors have occurred. When it is set to 1, an error has
occurred. By reading Register SIOCNT, this error flag is reset.
Additionally, when there has been an error, the data from the Receive Shift
Register is not written to the Receive Data Register. The conditions
associated with each error are described below.
ERROR NAME
Framing Error
Parity Error
Overrun Error
SIOCNT [d05] Receive Data Flag
When set to 0, there is still data present.
When set to 1, it is empty.
SIOCNT [d04] Send Data Flag
When set to 0, it is not full.
After one send operation ends this is reset.
When set to 1, it is full.
Set during a write of data to the lower 8 bits of the Send Data Register
SIODATA8
SIOCNT [d03] Parity Control
Switches between even parity and odd parity.
SIOCNT [d02] CTS Flag
The SD terminal of the other machine (receive enable/disable) is input to
the SC terminal.
When set to 0, a send is always possible independent of the SC Terminal.
When set to 1, a send is only possible when a LO is being input to the SC
Terminal.
©1999 - 2001 Nintendo of America Inc.
The receive data stop bit is not 0
When parity is enabled, there is an error in the parity for the receive data
When FIFO is invalid, if the receive data is not empty (SIOCNT[d05]=0)
and next receive has ended (detect stop bit). Or when FIFO is valid, if
receive FIFO is full and next communication has ended (detect stop bit).
146
CONDITION
Communication Functions
D.C.N. AGB-06-0001-002B4