SH7055S Datasheet, PDF (531/1002 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperH RISC engine Family/SH7000 Series

In receiving, the SCI operates as follows:
1. The SCI monitors the communication line. When it detects a start bit (0), the SCI synchronizes
internally and starts receiving.
2. Receive data is shifted into 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 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 RSR into RDR.
If the data passes these checks, the SCI sets RDRF to 1 and stores the receive data in RDR. If
one of the checks fails (receive error), the SCI operates as indicated in table 15.11.
Note: When a receive error occurs, further receiving is disabled. While receiving, the RDRF
bit is not set to 1, so 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 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 SCR is also set to 1, the
SCI requests a receive-error interrupt (ERI).
Table 15.11 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
Figure 15.9 shows an example of SCI receive operation in asynchronous mode.
Rev.2.0, 07/03, page 493 of 960