HD64F36022 datasheet(220/384 Pages) RENESAS

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Section 13 Serial Communication Interface 3 (SCI3)

Rev. 4.00 Sep. 23, 2005 Page 194 of 354

REJ09B0025-0400

13.4.3

Data Transmission

Figure 13.5 shows an example of operation for transmission in asynchronous mode. In

transmission, the SCI3 operates as described below.

1. The SCI3 monitors the TDRE flag in SSR. If the flag is cleared to 0, the SCI3 recognizes that

data has been written to TDR, and transfers the data from TDR to TSR.

2. After transferring data from TDR to TSR, the SCI3 sets the TDRE flag to 1 and starts

transmission. If the TIE bit is set to 1 at this time, a TXI interrupt request is generated.

Continuous transmission is possible because the TXI interrupt routine writes next transmit data

to TDR before transmission of the current transmit data has been completed.

3. The SCI3 checks the TDRE flag at the timing for sending the stop bit.

4. If the TDRE flag is 0, the data is transferred from TDR to TSR, the stop bit is sent, and then

serial transmission of the next frame is started.

5. If the TDRE flag is 1, the TEND flag in SSR is set to 1, the stop bit is sent, and then the “mark

state” is entered, in which 1 is output. If the TEIE bit in SCR3 is set to 1 at this time, a TEI

interrupt request is generated.

Figure 13.6 shows a sample flowchart for transmission in asynchronous mode.

1 frame

Start

bit

Start

bit

Transmit

data

Transmit

data

Parity

bit

Stop

bit

Parity

bit

Stop

bit

Mark

state

1 frame

1D0

0/1

0D0

0/1

Serial

data

TDRE

TEND

LSI

operation

TXI interrupt

request

generated

TDRE flag

cleared to 0

User

processing

Data written

to TDR

TXI interrupt request generated

TEI interrupt request

generated

Figure 13.5 Example of SCI3 Transmission in Asynchronous Mode

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

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