SH7144 Datasheet, PDF (442/773 Pages) Renesas Technology Corp – Hitachi SuperH RISC engine

13.6.4 Serial data reception (Clocked Synchronous mode)
Figure 13.18 shows an example of SCI operation for reception in clocked synchronous mode. In
serial reception, the SCI operates as described below.
1. The SCI performs internal initialization in synchronization with a synchronization clock input
or output, starts receiving data, and stores the received data in RSR.
2. If an overrun error (when reception of the next data is completed while the RDRF flag is still
set to 1) occurs, the ORER bit in SSR is set to 1. If the RIE bit in SCR is set to 1 at this time,
an ERI interrupt request is generated. Receive data is not transferred to RDR. The RDRF flag
remains to be set to 1.
3. If reception finishes successfully, the RDRF bit in SSR is set to 1, and receive data is
transferred to RDR. If the RIE bit in SCR is set to 1 at this time, an RXI interrupt request is
generated. Because the RXI interrupt processing routine reads the receive data transferred to
RDR before reception of the next receive data has finished, continuous reception can be
enabled.
Synchroniza-
tion clock
Serial data
RDRF
ORER
Bit 7 Bit 0
Bit 7 Bit 0 Bit 1
RXI interrupt
request
generated
RDR data read and
RDRF flag cleared
to 0 in RXI interrupt
processing routine
1 frame
RXI interrupt
request
generated
Bit 6 Bit 7
ERI interrupt
request generated
by overrun error
Figure 13.18 Example of SCI Operation in Reception
Rev. 2.0, 09/02, page 402 of 732