H8SLASH3028F datasheet(536/923 Pages) RENESAS

536 / 923 page

Rev. 2.00, 09/03, page 506 of 890

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

Description

Priority

ERI

Receive error (ORER, FER, or PER)

High

RXI

Receive data register full (RDRF)

TXI

Transmit data register empty (TDRE)

TEI

Transmit end (TEND)

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.

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