Hitachi SH7750 series Hardware Manual page 553

In serial reception, the SCI operates as described below.
1. The SCI monitors the transmission line, and if a 0 start bit is detected, performs internal
synchronization and starts reception.
2. The received data is stored in SCRSR1 in LSB-to-MSB order.
3. The parity bit and stop bit are received.
After receiving these bits, the SCI carries out the following checks.
a. Parity check: The SCI checks whether the number of 1-bits in the receive data agrees with
the parity (even or odd) set in the O/E bit in SCSMR1.
b. Stop bit check: The SCI checks whether the stop bit is 1. If there are two stop bits, only the
first is checked.
c. Status check: The SCI checks whether the RDRF flag is 0, indicating that the receive data
can be transferred from SCRSR1 to SCRDR1.
If all the above checks are passed, the RDRF flag is set to 1, and the receive data is stored in
SCRDR1.
If a receive error is detected in the error check, the operation is as shown in table 15.11.
Note: No further receive operations can be performed when a receive error has occurred. Also
note that the RDRF flag is not set to 1 in reception, and so the error flags must be cleared
to 0.
4. If the EIO bit in SCSPTR1 is cleared to 0 and the RIE bit in SCSCR1 is set to 1 when the
RDRF flag changes to 1, a receive-data-full interrupt (RXI) request is generated.
If the RIE bit in SCSCR1 is set to 1 when the ORER, PER, or FER flag changes to 1, a
receive-error interrupt (ERI) request is generated. A receive-data-full request is always output
to the DMAC when the RDRF flag changes to 1.
Table 15.11 Receive Error Conditions
Receive Error
Overrun error
Framing error
Parity error
Figure 15.11 shows an example of the operation for reception in asynchronous mode.
Rev. 4.0, 04/00, page 542 of 850
Abbreviation Condition
ORER Reception of next data is
completed while RDRF flag
in SCSSR1 is set to 1
FER Stop bit is 0
PER Received data parity differs
from that (even or odd) set
in SCSMR1
Data Transfer
Receive data is not transferred
from SCRSR1 to SCRDR1
Receive data is transferred
from SCRSR1 to SCRDR1
Receive data is transferred
from SCRSR1 to SCRDR1