SH7020 Datasheet, PDF (390/509 Pages) Renesas Technology Corp – SuperH™ RISC engine

In receiving, the SCI operates as follows:
1. The SCI monitors the receive data line. When it detects a start bit (0), the SCI synchronizes
internally and starts receiving.
2. Receive data is shifted into the RSR in order from the LSB to the MSB.
3. The parity bit and stop bit are received. After receiving these bits, the SCI makes the following
checks:
a. Parity check: The number of 1s in the receive data must match the even or odd parity
setting of the O/E bit in the SMR.
b. Stop bit check: The stop bit value must be 1. If there are two stop bits, only the first stop bit
is checked.
c. Status check: RDRF must be 0 so that receive data can be loaded from the RSR into the
RDR.
If these checks all pass, the SCI sets RDRF to 1 and stores the received data in the RDR. If one
of the checks fails (receive error), the SCI operates as indicated in table 13.11.
Note: When a receive error flag is set, further receiving is disabled. The RDRF bit is not set
to 1. Be sure to clear the error flags.
4. After setting RDRF to 1, if the receive-data-full interrupt enable bit (RIE) is set to 1 in the
SCR, the SCI requests a receive-data-full interrupt (RXI). If one of the error flags (ORER,
PER, or FER) is set to 1 and the receive-data-full interrupt enable bit (RIE) in the SCR is also
set to 1, the SCI requests a receive-error interrupt (ERI).
Figure 13.8 shows an example of SCI receive operation in the asynchronous mode.
Table 13.11 Receive Error Conditions and SCI Operation
Receive Error
Overrun error
Framing error
Parity error
Abbreviation
ORER
FER
PER
Condition
Data Transfer
Receiving of next data ends while Receive data not loaded
RDRF is still set to 1 in SSR
from RSR into RDR
Stop bit is 0
Receive data loaded from
RSR into RDR
Parity of receive data differs from Receive data loaded from
even/odd parity setting in SMR RSR into RDR
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