HD6413008VF25 Datasheet, PDF (407/688 Pages) Renesas Technology Corp – Old Company Name in Catalogs and Other Documents

12. Serial Communication Interface
In receiving, the SCI operates as follows:
• The SCI monitors the communication line. When it detects a start bit (0 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 these bits, the SCI carries out the following checks:
⎯ Parity check: The number of 1s in the receive data must match the even or odd parity
setting of in the O/E bit in SMR.
⎯ Stop bit check: The stop bit value must be 1. If there are two stop bits, only the first is
checked.
⎯ Status check: The RDRF flag must be 0, indicating that the receive data can be transferred
from RSR into RDR.
If these all checks 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 shown in table 12.11.
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 to 0.
• 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 12.11 Receive Error Conditions
Receive Error Abbreviation Condition
Data Transfer
Overrun error ORER
Receiving of next data ends while Receive data is not transferred
RDRF flag is still set to 1 in SSR from RSR to RDR
Framing error FER
Stop bit is 0
Receive data is transferred from
RSR to RDR
Parity error PER
Parity of received data differs from Receive data is transferred from
even/odd parity setting in SMR RSR to RDR
Rev.4.00 Aug. 20, 2007 Page 361 of 638
REJ09B0395-0400