SH7058 Datasheet, PDF (556/1130 Pages) Renesas Technology Corp – Renesas SuperHTM RISC engine

15.4 SCI Interrupt Sources and the DMAC
The SCI has four interrupt sources: transmit-end (TEI), receive-error (ERI), receive-data-full
(RXI), and transmit-data-empty (TXI). Table 15.12 lists the interrupt sources and indicates their
priority. These interrupts can be enabled and disabled by the TIE, RIE, and TEIE bits in the serial
control register (SCR). Each interrupt request is sent separately to the interrupt controller.
TXI is requested when the TDRE bit in SSR is set to 1. TXI can start the direct memory access
controller (DMAC) to transfer data. TDRE is automatically cleared to 0 when the DMAC writes
data in the transmit data register (TDR).
RXI is requested when the RDRF bit in SSR is set to 1. RXI can start the DMAC to transfer data.
RDRF is automatically cleared to 0 when the DMAC reads the receive data register (RDR).
ERI is requested when the ORER, PER, or FER bit in SSR is set to 1. ERI cannot start the DMAC.
TEI is requested when the TEND bit in SSR is set to 1. TEI cannot start the DMAC. Where the
TXI interrupt indicates that transmit data writing is enabled, the TEI interrupt indicates that the
transmit operation is complete.
Table 15.12 SCI Interrupt Sources
Interrupt Source
ERI
RXI
TXI
TEI
Description
Receive error (ORER, PER, or FER)
Receive data full (RDRF)
Transmit data empty (TDRE)
Transmit end (TEND)
DMAC Activation
No
Yes
Yes
No
Priority
High
Low
15.5 Usage Notes
Sections 15.5.1 to 15.5.9 provide information concerning use of the SCI.
15.5.1 TDR Write and TDRE Flag
The TDRE bit in the serial status register (SSR) is a status flag indicating loading of transmit data
from TDR into TSR. The SCI sets TDRE to 1 when it transfers data from TDR to TSR. Data can
be written to TDR regardless of the TDRE bit status. If new data is written in TDR when TDRE is
0, however, the old data stored in TDR will be lost because the data has not yet been transferred to
TSR. Before writing transmit data to TDR, be sure to check that TDRE is set to 1.
Rev. 3.0, 09/04, page 515 of 1086