HD6417750RF240V Datasheet, PDF(379/606 Page) Renesas Technology Corp – Renesas 16-Bit Single-Chip Microcomputer H8S Family/H8S/2600 Series

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HD6417750RF240V Datasheet, PDF (379/606 Pages) Renesas Technology Corp – Renesas 16-Bit Single-Chip Microcomputer H8S Family/H8S/2600 Series

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Section 14 Serial Communication Interface (SCI)

14.4.5 Data Transmission (Asynchronous Mode)

Figure 14.6 shows an example of operation for transmission in asynchronous mode. In

transmission, the SCI operates as described below.

1. The SCI monitors the TDRE flag in SSR. If the flag is cleared to 0, the SCI 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 SCI sets the TDRE flag to 1 and starts

transmission. If the TIE bit is set to 1 at this time, a transmit data empty interrupt request (TXI)

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. Data is sent from the TxD pin in the following order: start bit, transmit data, parity bit or

multiprocessor bit (may be omitted depending on the format), and stop bit.

4. The SCI checks the TDRE flag at the timing for sending the stop bit.

5. 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.

6. If the TDRE flag is 1, the TEND flag in SSR is set to 1, the stop bit is sent, and then the âmark

stateâ is entered, in which 1 is output. If the TEIE bit in SCR is set to 1 at this time, a TEI

interrupt request is generated.

Figure 14.7 shows a sample flowchart for transmission in asynchronous mode.

Start

Data

Parity Stop Start

Data

Parity Stop

1 bit

bit bit bit

bit bit 1

0 D0 D1

D7 0/1 1 0 D0 D1

D7 0/1

1

Idle state

(mark state)

TDRE

TEND

TXI interrupt

Data written to TDR and TXI interrupt

request generated TDRE flag cleared to 0 in request generated

TXI interrupt service routine

TEI interrupt

request generated

1 frame

Figure 14.6 Example of Operation in Transmission in Asynchronous Mode

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

Rev. 7.00 Sep. 11, 2009 Page 343 of 566

REJ09B0211-0700

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