H8SSLASH2218 datasheet(458/750 Pages) RENESAS

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Section 12 Serial Communication Interface

Rev.6.00 Jun. 03, 2008 Page 410 of 698

REJ09B0074-0600

12.4.6

Serial Data Reception (Asynchronous Mode)

Figure 12.11 shows an example of operation for reception in asynchronous mode. In serial

reception, the SCI operates as described below.

1. The SCI monitors the communication line. If a start bit is detected, the SCI performs internal

synchronization, receives receive data in RSR, and checks the parity bit and stop bit.

2. If an overrun error occurs (when reception of the next data is completed while the RDRF flag

is still set to 1), the ORER bit in SSR is set to 1. If the RIE bit in SCR is set to 1 at this time, an

ERI interrupt request is generated. Receive data is not transferred to RDR. The RDRF flag

remains to be set to 1.

3. If a parity error is detected, the PER bit in SSR is set to 1 and receive data is transferred to

RDR. If the RIE bit in SCR is set to 1 at this time, an ERI interrupt request is generated.

4. If a framing error is detected (when the stop bit is 0), the FER bit in SSR is set to 1 and receive

data is transferred to RDR. If the RIE bit in SCR is set to 1 at this time, an ERI interrupt

request is generated.

5. If reception is completed successfully, the RDRF bit in SSR is set to 1, and receive data is

transferred to RDR. If the RIE bit in SCR is set to 1 at this time, an RXI interrupt request is

generated. Continuous reception is possible because the RXI interrupt routine reads the receive

data transferred to RDR before reception of the next receive data has been completed.

RDRF

FER

1 frame

0/1

Data

Start

bit

Parity

bit

Stop

bit

Start

bit

Data

Parity

bit

Stop

bit

ERI interrupt request

generated by framing

error

Idle state

(mark state)

RDR data read and RDRF

flag cleared to 0 in RXI

interrupt service routine

RXI interrupt

request

generated

Figure 12.11 Example of SCI Operation in Reception

(Example with 8-Bit Data, Parity, One Stop Bit)

Table 12.11 shows the states of the SSR status flags and receive data handling when a receive error

is detected. If a receive error is detected, the RDRF flag retains its state before receiving data.

Reception cannot be resumed while a receive error flag is set to 1. Accordingly, clear the ORER,

FER, PER, and RDRF bits to 0 before resuming reception. Figure 12.12 shows a sample flow chart

for serial data reception.

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