Section 12 Serial Communication Interface (SCI)
Rev. 3.00 Sep. 27, 2007 Page 471 of 758
REJ09B0243-0300
12.7 Usage
Notes
12.7.1
SCTDR Writing and TDRE Flag
The TDRE flag in the serial status register (SCSSR) is a status flag indicating transferring of
transmit data from SCTDR into SCTSR. The SCI sets the TDRE flag to 1 when it transfers data
from SCTDR to SCTSR.
Data can be written to SCTDR regardless of the TDRE bit status.
If new data is written in SCTDR when TDRE is 0, however, the old data stored in SCTDR will be
lost because the data has not yet been transferred to SCTSR. Before writing transmit data to
SCTDR, be sure to check that the TDRE flag is set to 1.
12.7.2
Multiple Receive Error Occurrence
If multiple receive errors occur at the same time, the status flags in SCSSR are set as shown in
table 12.18. When an overrun error occurs, data is not transferred from the receive shift register
(SCRSR) to the receive data register (SCRDR) and the received data will be lost.
Table 12.18 SCSSR Status Flag Values and Transfer of Received Data
SCSSR Status Flags
Receive Errors Generated
RDRF
ORER FER
PER
Receive Data
Transfer from
SCRSR to
SCRDR
Overrun
error
1 1 0 0 Not
transferred
Framing
error
0 0 1 0 Transferred
Parity
error
0 0 0 1 Transferred
Overrun
error
+
framing
error
1 1 1 0 Not
transferred
Overrun
error
+
parity
error
1 1 0 1 Not
transferred
Framing
error
+
parity
error
0 0 1 1 Transferred
Overrun error + framing error + parity error 1
1
1
1
Not transferred
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