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Chapter 32 USART (LIN / FIFO)
4.USART Registers
Table 4-5 Functions of each bit of status register 04 (SSR04)
Bit name Function
bit15 PE: Parity error
flag bit
• This bit is set to 1 when a parity error occurs during reception and is
cleared when 0 is written to the CRE bit of the serial control register
(SCR04).
• A reception interrupt request is output when this bit and the RIE bit are 1.
• Data in the reception data register (RDR04) is invalid when this flag is set.
bit14 ORE: Overrun
error flag bit
• This bit is set to 1 when an overrun error occurs during reception and is
cleared when 0 is written to the CRE bit of the serial control register
(SCR04).
• A reception interrupt request is output when this bit and the RIE bit are 1.
• Data in the reception data register (RDR04) is invalid when this flag is set.
bit13 FRE: Framing
error flag bit
• This bit is set to 1 when a framing error occurs during reception and is
cleared when 0 is written to the CRE bit of the serial control register 1
(SCR04).
• A reception interrupt request is output when this bit and the RIE bit are 1.
• Data in the reception data register (RDR04) is invalid when this flag is set.
bit12 RDRF: Receive
data full flag bit
• This flag indicates the status of the reception data register (RDR04).
• This bit is set to 1 when reception data is loaded into RDR04 and can only
be cleared to 0 when the reception data register (RDR04) is read.
• A reception interrupt request is output when this bit and the RIE bit are 1.
bit11 TDRE:
Transmission
data empty flag
bit
• This flag indicates the status of the transmission data register (TDR04).
• This bit is cleared to 0 when transmission data is written to TDR04 and is
set to 1 when data is loaded into the transmission shift register and
transmission starts.
• A transmission interrupt request is generated if this bit and the RIE bit are
1.
<Caution>
This bit is set to 1 (TDR04 empty) as its initial value.
bit10 BDS: Transfer
direction selection
bit
• This bit selects whether to transfer serial data from the least significant bit
(LSB first, BDS=0) or the most significant bit (MSB first, BDS=1).
<Caution>
The high-order and low-order sides of serial data are interchanged with
each other during reading from or writing to the serial data register. If this
bit is set to another value after the data is written to the RDR04 register,
the data becomes invalid.
This bit is fixed to 0 in mode 3 (LIN)
bit9 RIE: Reception
interrupt request
enable bit
• This bit enables or disables input of a request for transmission interrupt to
the CPU.
• A reception interrupt request is output when this bit and the reception data
flag bit (RDRF) are 1 or this bit and one or more error flag bits (PE, ORE,
and FRE) are 1.