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Receiving Serial Data (Asynchronous Mode): Figure 11-7 shows a sample flowchart for
receiving serial data and indicates the procedure to follow.
Initialize
Start receiving
Read ORER, PER,
and FER flags in SSR
∨
PER
ORER = 1?
Read RDRF flag in SSR
No
RDRF = 1?
Read receive data
from RDR, and clear
RDRF flag to 0 in SSR
No
Finished
receiving?
Clear RE bit to 0 in SCR
End
Figure 11-7 Sample Flowchart for Receiving Serial Data (1)
358
1
2
∨
Yes
FER
No
Error handling
(continued on next page)
4
Yes
5
Yes
1.
SCI initialization: the receive data function of
the RxD pin is selected automatically.
2., 3.
Receive error handling and break
detection: if a receive error occurs, read the
ORER, PER, and FER flags in SSR to identify
the error. After executing the necessary error
handling, clear the ORER, PER, and FER
flags all to 0. Receiving cannot resume if any
of the ORER, PER, and FER flags remains
set to 1. When a framing error occurs, the
RxD pin can be read to detect the break state.
4.
SCI status check and receive data read: read
3
SSR, check that RDRF is set to 1, then read
receive data from RDR and clear the RDRF
flag to 0. Notification that the RDRF flag has
changed from 0 to 1 can also be given by the
RXI interrupt.
5.
To continue receiving serial data: check the
RDRF flag, read RDR, and clear the RDRF
flag to 0 before the stop bit of the current
frame is received.
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