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Rev. 1.00, 05/04, page 241 of 544
12.3.7 Serial Status Register (SSR)
SSR is a register containing status flags of the SCI and multiprocessor bits for transfer. TDRE,
RDRF, ORER, PER, and FER can only be cleared.
Bit Bit Name
Initial
Value R/W Description
7 TDRE 1 R/(W)* Transmit Data Register Empty
Indicates whether TDR contains transmit data.
[Setting conditions]
• When the TE bit in SCR is 0
• When data is transferred from TDR to TSR and
TDR is ready for data write
[Clearing conditions]
• When 0 is written to TDRE after reading TDRE = 1
6 RDRF 0 R/(W)* Receive Data Register Full
Indicates that receive data is stored in RDR.
[Setting condition]
• When serial reception ends normally and receive
data is transferred from RSR to RDR
[Clearing conditions]
• When 0 is written to RDRF after reading RDRF = 1
The RDRF flag is not affected and retains its previous
value when the RE bit in SCR is cleared to 0.
5 ORER 0 R/(W)* Overrun Error
[Setting condition]
• When the next data is received while RDRF = 1
[Clearing condition]
• When 0 is written to ORER after reading ORER = 1
4 FER 0 R/(W)* Framing Error
[Setting condition]
• When the stop bit is 0
[Clearing condition]
• When 0 is written to FER after reading FER = 1
In 2-stop-bit mode, only the first stop bit is checked.