SH7708 datasheet(390/633 Pages) RENESAS

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Figure 13.6 shows an example of SCI transmit operation in asynchronous mode.

0/1

TDRE

TEND

Parity

bit

Parity

bit

Serial

data

Start

bit

Data

Stop

bit

Start

bit

Data

Stop

bit

Idle

(mark)

state

TXI interrupt

request

TEI interrupt

request

TXI interrupt

handler writes

data to SCTDR

and clears TDRE

bit to 0

1 frame

0/1

TXI interrupt

request

Figure 13.6 SCI Transmit Operation in Asynchronous Mode (Example: 8-Bit Data with

Parity and One Stop Bit)

Receiving Serial Data (Asynchronous Mode): Figure 13.7 shows a sample flowchart for

receiving serial data. The procedure for receiving serial data after enabling the SCI for reception

is:

1. Receive error handling and break detection: If a receive error occurs, read the ORER, PER and

FER bits in SCSSR to identify the error. After executing the necessary error handling, clear

ORER, PER and FER all to 0. Receiving cannot resume if ORER, PER or FER remain set to 1.

When a framing error occurs, the RxD pin can be read to detect the break state.

2. SCI status check and receive-data read: Read the serial status register (SCSSR), check that

RDRF is set to 1, then read receive data from the receive data register (SCRDR) and clear

RDRF to 0. The RXI interrupt can also be used to determine if the RDRF bit has changed from

0 to 1.

3. To continue receiving serial data: Read the RDRF and SCRDR bits and clear RDRF to 0

before the stop bit of the current frame is received.

SH7708 Datenblatt(PDF) 390 Page - Renesas Technology Corp

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