HD64F2357VF13 Datasheet, PDF (544/1049 Pages) Renesas Technology Corp – Old Company Name in Catalogs and Other Documents

14.5 Usage Notes
The following points should be noted when using the SCI.
Relation between Writes to TDR and the TDRE Flag
The TDRE flag in SSR is a status flag that indicates that transmit data has been transferred from TDR to TSR. When the
SCI transfers data from TDR to TSR, the TDRE flag is set to 1.
Data can be written to TDR regardless of the state of the TDRE flag. However, if new data is written to TDR when the
TDRE flag is cleared to 0, the data stored in TDR will be lost since it has not yet been transferred to TSR. It is therefore
essential to check that the TDRE flag is set to 1 before writing transmit data to TDR.
Operation when Multiple Receive Errors Occur Simultaneously
If a number of receive errors occur at the same time, the state of the status flags in SSR is as shown in table 14-13. If there
is an overrun error, data is not transferred from RSR to RDR, and the receive data is lost.
Table 14-13 State of SSR Status Flags and Transfer of Receive Data
RDRF
1
0
0
1
1
0
1
ORER
1
0
0
1
1
0
1
SSR Status Flags
FER PER RSR to RDR
0
0
×
1
0
0
1
1
0
×
0
1
×
1
1
1
1
×
Notes: : Receive data is transferred from RSR to RDR.
×: Receive data is not transferred from RSR to RDR.
Receive Data Transfer
Receive Error Status
Overrun error
Framing error
Parity error
Overrun error + framing error
Overrun error + parity error
Framing error + parity error
Overrun error + framing error +
parity error
Rev.6.00 Oct.28.2004 page 514 of 1016
REJ09B0138-0600H