H8S2245 datasheet(485/818 Pages) RENESAS

485 / 818 page

Section 12 Serial Communication Interface (SCI)

Rev.3.00 Mar. 26, 2007 Page 443 of 772

REJ09B0355-0300

In serial reception, the SCI operates as described below.

[1] The SCI monitors the transmission line, and if a 0 stop bit is detected, performs internal

synchronization and starts reception.

[2] The received data is stored in RSR 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 SMR.

[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 RSR to RDR.

If all the above checks are passed, the RDRF flag is set to 1, and the receive data is stored in

RDR.

If a receive error* is detected in the error check, the operation is as shown in table 12.11.

Note: *

Subsequent receive operations cannot 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 RIE bit in SCR is set to 1 when the RDRF flag changes to 1, a receive data full interrupt

(RXI) request is generated.

Also, if the RIE bit in SCR is set to 1 when the ORER, PER, or FER flag changes to 1, a

receive error interrupt (ERI) request is generated.

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