SH7125_08 Datasheet, PDF (491/774 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperH™ RISC engine Family

Section 12 Serial Communication Interface (SCI)
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
Overrun error
1
1
0
0
Framing error
0
0
1
0
Parity error
0
0
0
1
Overrun error + framing error
1
1
1
0
Overrun error + parity error
1
1
0
1
Framing error + parity error
0
0
1
1
Overrun error + framing error + parity error 1
1
1
1
Receive Data
Transfer from
SCRSR to
SCRDR
Not transferred
Transferred
Transferred
Not transferred
Not transferred
Transferred
Not transferred
Rev. 4.00 Jul. 25, 2008 Page 471 of 750
REJ09B0243-0400