H8SLASH3021 datasheet(390/712 Pages) RENESAS

390 / 712 page

11. Serial Communication Interface

Rev.2.00 Mar. 22, 2007 Page 366 of 684

REJ09B0352-0200

Transmitting Serial Data (Asynchronous Mode): Figure 11.5 shows a sample flowchart for

transmitting serial data and indicates the procedure to follow.

Start transmitting

Read TDRE flag in SSR

TDRE = 1?

Write transmit data

in TDR and clear TDRE

flag to 0 in SSR

All data

transmitted?

End

Yes

Read TEND flag in SSR

TEND = 1?

Yes

Output break

signal?

Yes

Clear TE bit to 0 in SCR

Clear DR bit to 0,

set DDR bit to 1

Initialize

1. SCI initialization: the transmit data output function

of the TxD pin is selected automatically. After the TE bit

is set to 1, one frame of 1s is output, then transmission is

possible.

2. SCI status check and transmit data write: read SSR,

check that the TDRE flag is 1, then write transmit data

in TDR and clear the TDRE flag to 0.

3. To continue transmitting serial data: after checking

that the TDRE flag is 1, indicating that data can be

written, write data in TDR, then clear the TDRE

flag to 0.

4. To output a break signal at the end of serial transmission:

set the DDR bit to 1 and clear the DR bit to 0

(DDR and DR are I/O port registers), then clear the

TE bit to 0 in SCR.

Figure 11.5 Sample Flowchart for Transmitting Serial Data

H8/3021 Datasheet(PDF) 390 Page - Renesas Technology Corp