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Section 10 Serial Communication Interface
SCI3 operates as follows when receiving data.
SCI3 performs internal synchronization and begins reception in synchronization with the serial
clock input or output.
The received data is placed in RSR in LSB-to-MSB order.
After the data has been received, SCI3 checks that bit RDRF is set to 0, indicating that the receive
data can be transferred from RSR to RDR.
If this check shows that there is no overrun error, bit RDRF is set to 1, and the receive data is
stored in RDR. If bit RIE is set to 1 in SCR3, an RXI interrupt is requested. If the check
identifies an overrun error, bit OER is set to 1.
Bit RDRF remains set to 1. If bit RIE is set to 1 in SCR3, an ERI interrupt is requested.
See table 10.15 for the conditions for detecting a receive error, and receive data processing.
Note: No further receive operations are possible while a receive error flag is set. Bits OER,
FER, PER, and RDRF must therefore be cleared to 0 before resuming reception.
Figure 10.19 shows an example of the operation when receiving in synchronous mode.
Serial
clock
Serial
Bit 7
data
RDRF
OER
LSI
RXI request
operation
User
processing
Figure 10.19 Example of Operation when Receiving in Synchronous Mode
Rev. 6.00 Aug 04, 2006 page 394 of 680
REJ09B0145-0600
Bit 0
Bit 7
1 frame
RDRE cleared
to 0
RDR data read
Bit 0
Bit 1
1 frame
RXI request
RDR data has
not been read
(RDRF = 1)
Bit 6
Bit 7
ERI request in
response to
overrun error
Overrun error
processing
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