3874 Group User's Manual
APPLICATION
2-79
2.5 Serial I/O
s Receive buffer full flag (bit 1)
When all receive data has been input to the receive shift register and then this receive data is
transferred to the receive buffer register, this flag is automatically set to “1.”
When the transferred receive data is read out from the receive buffer register, the flag is automatically
cleared to “0.”
If all the next receive data is input to the receive shift register when the receive buffer full flag is
“1” (the receive buffer register has not been read out), the overrun error flag T is set to “1.”
This flag is valid in both the clock synchronous mode and the UART mode.
T: bit 3 of serial I/O1 status register
s Transmit shift register shift completion flag (bit 2)
When a shift operation (transmission of the first data bit) starts with a synchronous clock after
transmit data of the transmit shift register is transferred, this flag is cleared to “0.” When the shift
operation is completed (completion of transmission of the last data bit), the flag is set to “1.”
This flag is valid in both the clock synchronous mode and the UART mode.
s Overrun error flag (bit 3)
If all the next receive data is input to the receive shift register when the receive buffer register
contains the data (not read out), this flag is set to “1” (occurrence of an overrun error). This flag
is set to “0” by one of the following operations.
Set “0” to the serial I/O1 enable bitT1
Set “0” to the receive enable bitT2
Write data (arbitrary) into the serial I/O1 status register
This flag is valid in both the clock synchronous mode and the UART mode.
T1: bit 7 of serial I/O1 control register
T2: bit 5 of serial I/O1 control register
s Parity error flag (bit 4)
In the UART mode, this flag checks an even parity or odd parity by hardware.
When the parity of received data is different from the set parity, this flag is set to “1.”
This flag is set to “0” by one of the following operations.
Set “0” to the serial I/O1 enable bitT1
Set “0” to the receive enable bitT2
Write data (arbitrary) into the serial I/O1 status register
This flag is valid only in the parity enable state in the UART mode.
T1: bit 7 of serial I/O1 control register
T2: bit 5 of serial I/O1 control register
s Framing error flag (bit 5)
In the UART mode, this flag judges whether frame synchronization is abnormal.
When the stop bit of receive data cannot be received at the set timing, this flag is set to “1.”
This flag is set to “0” by one of the following operations.
Set “0” to the serial I/O1 enable bitT1
Set “0” to the receive enable bitT2
Write data (arbitrary) into the serial I/O1 status register
This flag is valid only in the UART mode.
T1: bit 7 of serial I/O1 control register
T2: bit 5 of serial I/O1 control register