Rev. 1.0, 02/00, page 448 of 1141
In serial reception, the SCI operates as described below.
1. The SCI performs internal initialization in synchronization with serial clock input or output.
2. The received data is stored in RSR1 in LSB-to-MSB order.
After reception, the SCI checks whether the RDRF flag is 0 and the receive data can be
transferred from RSR1 to RDR1.
If this check is passed, the RDRF flag is set to 1, and the receive data is stored in RDR1. If a
receive error is detected in the error check, the operation is as shown in table 22.11.
Neither transmit nor receive operations can be performed subsequently when a receive error
has been found in the error check.
3. If the RIE bit in SCR1 is set to 1 when the RDRF flag changes to 1, a receive-data-full
interrupt (RXI) request is generated.
Also, if the RIE bit in SCR1 is set to 1 when the ORER flag changes to 1, a receive-error
interrupt (ERI) request is generated.
Figure 22.21 shows an example of SCI operation in reception.
Bit 7
Serial
data
Synchronous
clock
1 frame
RDRF
ORER
ERI interrupt request
generated by
overrun error
RXI interrupt
request
generated
RDR1 data read and
RDRF flag cleared to 0
in RXI interrupt
handling routine
RXI interrupt
request
generated
Bit 0
Bit 7
Bit 0
Bit 1
Bit 6
Bit 7
Figure 22.21 Example of SCI Operation in Reception