3069RF-ZTAT Datasheet, PDF (530/1003 Pages) Renesas Technology Corp – RENESAS 16-BIT SINGLE-CHIP MICROCOMPUTER

13.4 SCI Interrupts
The SCI has four interrupt request sources: the transmit-end interrupt (TEI), receive-error
interrupt (ERI), receive-data-full interrupt (RXI), and transmit-data-empty interrupt (TXI). Table
13.12 lists the interrupt sources and indicates their priority. These interrupts can be enabled or
disabled by the TIE, RIE, and TEIE bits in SCR. Each interrupt request is sent separately to the
interrupt controller.
A TXI interrupt is requested when the TDRE flag is set to 1 in SSR. A TEI interrupt is requested
when the TEND flag is set to 1 in SSR. A TXI interrupt request can activate the DMAC to transfer
data. Data transfer by the DMAC automatically clears the TDRE flag to 0. A TEI interrupt request
cannot activate the DMAC.
An RXI interrupt is requested when the RDRF flag is set to 1 in SSR. An ERI interrupt is
requested when the ORER, PER, or FER flag is set to 1 in SSR. An RXI interrupt can activate the
DMAC to transfer data. Data transfer by the DMAC automatically clears the RDRF flag to 0. An
ERI interrupt request cannot activate the DMAC.
The DMAC can be activated by interrupts from SCI channel 0.
Table 13.12 SCI Interrupt Sources
Interrupt Source
ERI
RXI
TXI
TEI
Description
Receive error (ORER, FER, or PER)
Receive data register full (RDRF)
Transmit data register empty (TDRE)
Transmit end (TEND)
Priority
High
Low
13.5 Usage Notes
13.5.1 Notes on Use of SCI
Note the following points when using the SCI.
TDR Write and TDRE Flag: The TDRE flag in SSR is a status flag indicating the loading of
transmit data from TDR to TSR. The SCI sets the TDRE flag to 1 when it transfers data from
TDR to TSR.
Data can be written into TDR regardless of the state of the TDRE flag. If new data is written in
TDR when the TDRE flag is 0, the old data stored in TDR will be lost because this data has not
yet been transferred to TSR. Before writing transmit data in TDR, be sure to check that the TDRE
flag is set to 1.
Rev. 5.0, 09/04, page 508 of 978