HD6433635SW datasheet(267/418 Pages) RENESAS

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SCI3 operates as follows when receiving serial data in asynchronous mode.

SCI3 monitors the communication line, and when a start bit (0) is detected it performs internal

synchronization and starts receiving. The communication format for data receiving is as outlined

in table 10.14. Received data is set in RSR in order of LSB to MSB, then the parity bit and stop

bit(s) are received. After receiving the data, SCI3 performs the following checks:

• Parity check: The number of 1s in receive data is checked to see if it matches the odd or even

parity selected in bit PM of SMR.

• Stop bit check: The stop bit is checked for a value of 1. If there are two stop bits, only the first

bit is checked.

• Status check: The RDRF bit is checked for a value of 0 to make sure received data can be

transferred from RSR to RDR.

If no receive error is detected by the above checks, bit RDRF is set to 1 and the received data is

stored in RDR. At that time, if bit RIE in SCR3 is set to 1, an RXI interrupt is requested. If the

error check detects a receive error, the appropriate error flag (OER, PER, or FER) is set to 1.

RDRF retains the same value as before the data was received. If at this time bit RIE in SCR3 is set

to 1, an ERI interrupt is requested.

Table 10.15 gives the receive error detection conditions and the processing of received data in

each case.

Note:

Data receiving cannot be continued while a receive error flag is set. Before continuing the

receive operation it is necessary to clear the OER, FER, PER, and RDRF flags to 0.

Table 10.15 Receive Error Conditions and Received Data Processing

Receive Error

Abbrev.

Detection Conditions

Received Data Processing

Overrun error

OER

Receiving of the next data ends while

bit RDRF in SSR is still set to 1

Received data is not

transferred from RSR to RDR

Framing error

FER

Stop bit is 0

Received data is transferred

from RSR to RDR

Parity error

PER

Received data does not match the

parity (odd/even) set in SMR

Received data is transferred

from RSR to RDR

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