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In receiving, the SCI operates as follows.
• The SCI monitors the receive data line. When it detects a start bit, the SCI synchronizes
internally and starts receiving.
• Receive data is stored in RSR in order from LSB to MSB.
• The parity bit and stop bit are received.
After receiving data, the SCI makes the following checks:
Parity check:
Stop bit check:
Status check:
If these checks all pass, the RDRF flag is set to 1 and the received data is stored in RDR. If one of
the checks fails (receive error), the SCI operates as indicated in table 11-11.
Note: When a receive error occurs, further receiving is disabled. In receiving, the RDRF flag is
not set to 1. Be sure to clear the error flags.
• When the RDRF flag is set to 1, if the RIE bit is set to 1 in SCR, a receive-data-full interrupt
(RXI) is requested. If the ORER, PER, or FER flag is set to 1 and the RIE bit in SCR is also set
to 1, a receive-error interrupt (ERI) is requested.
Table 11-11 Receive Error Conditions
Receive Error
Ab br e v i a t i on
Overrun error
ORER
Framing error
FER
Parity error
PER
364
The number of 1s in the receive data must match the even or odd parity
setting of the O/E bit in SMR.
The stop bit value must be 1. If there are two stop bits, only the first
stop bit is checked.
The RDRF flag must be 0 so that receive data can be transferred from
RSR into RDR.
Condition
Receiving of next data ends
while RDRF flag is still set to
1 in SSR
Stop bit is 0
Parity of receive data differs
from even/odd parity setting
in SMR
Data Transfer
Receive data not transferred
from RSR to RDR
Receive data transferred
from RSR to RDR
Receive data transferred
from RSR to RDR
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