HD6432351 datasheet(640/1025 Pages) RENESAS

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Section 13 Serial Communication Interface (SCI)

Rev. 3.00 Sep 15, 2006 page 606 of 988

REJ09B0330-0300

13.5

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 13.13. If there is an overrun error, data is not transferred from RSR to RDR, and

the receive data is lost.

Table 13.13 State of SSR Status Flags and Transfer of Receive Data

SSR Status Flags

RDRF

ORER

FER

PER

Receive Data Transfer

RSR to RDR

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

Notes:

: Receive data is transferred from RSR to RDR.

X: Receive data is not transferred from RSR to RDR.

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