H8SSLASH2214 datasheet(580/936 Pages) RENESAS

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Section 12 Serial Communication Interface (SCI)

Rev.4.00 Sep. 18, 2008 Page 520 of 872

REJ09B0189-0400

12.5

Usage Notes

The following points should be noted when using the SCI.

(1) Module Stop Mode Settings

The SCI module operation disabled/enabled state can be set with the module stop control register.

The initial value of this register sets the SCI module to the stopped state. Register access becomes

possible when module stop mode is cleared. See section 17, Power-Down Modes, for details.

(2) 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.

(3) 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 12.14. If there is an overrun error, data is not transferred from RSR to RDR, and

the receive data is lost.

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