Datasheet

Section 15 Serial Communication Interface (SCI)
Rev. 6.00 Mar. 18, 2010 Page 606 of 982
REJ09B0054-0600
15.6.4 Serial Data Reception (Clocked Synchronous Mode)
Figure 15.21 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 synchronous with a synchronous clock input or output,
starts receiving data, and stores the received data in RSR.
2. If an overrun error occurs (when reception of the next data is completed while the RDRF flag
in SSR is still set to 1), 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, and the
RDRF flag remains to be set to 1.
3. If reception is completed 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. Continuous reception is possible because the RXI interrupt routine reads the
receive data transferred to RDR before reception of the next receive data has finished.
Bit 7
Serial data
Synchronization
clock
1 frame
RDRF
ORER
ERI interrupt request
generated by overrun
error
RXI interrupt
request generated
RDR data read and
RDRF flag cleared
to 0 in RXI interrupt
RXI interrupt
request
generated
Bit 0 Bit 7 Bit 0 Bit 1 Bit 6 Bit 7
Figure 15.21 Example of SCI Operation in Reception
Reception cannot be resumed while a receive error flag is set to 1. Accordingly, clear the ORER,
FER, PER, and RDRF bits to 0 before resuming reception. Figure 15.22 shows a sample flow
chart for serial data reception.
An overrun error occurs or synchronous clocks are output until the RE bit is cleared to 0 when an
internal clock is selected and only receive operation is possible. When a transmission and
reception will be carried out in a unit of one frame, be sure to carry out a dummy transmission
with only one frame by the simultaneous transmit and receive operations at the same time.