HD64F2149YV datasheet(488/1075 Pages) RENESAS

488 / 1075 page

Section 15 Serial Communication Interface (SCI, IrDA)

Rev. 3.00 Jan 18, 2006 page 460 of 1044

REJ09B0280-0300

Serial Data Transmission (Asynchronous Mode): Figure 15.5 shows a sample flowchart for

serial transmission.

The following procedure should be used for serial data transmission.

<End>

[1]

Yes

Initialization

Start transmission

Read TDRE flag in SSR

[2]

Write transmit data to TDR

and clear TDRE flag in SSR to 0

Yes

Read TEND flag in SSR

[3]

Yes

[4]

Clear DR to 0 and

set DDR to 1

Clear TE bit in SCR to 0

TDRE = 1?

All data transmitted?

TEND = 1?

Break output?

[1] SCI initialization:

The TxD pin is automatically

designated as the transmit data

output pin.

After the TE bit is set to 1, one

frame of 1s is output and

transmission is enabled.

[2] SCI status check and transmit data

write:

Read SSR and check that the

TDRE flag is set to 1, then write

transmit data to TDR and clear the

TDRE flag to 0.

[3] Serial transmission continuation

procedure:

To continue serial transmission,

read 1 from the TDRE flag to

confirm that writing is possible,

then write data to TDR, and then

clear the TDRE flag to 0. Checking

and clearing of the TDRE flag is

automatic when the DTC is

activated by a transmit-data-empty

interrupt (TXI) request, and data is

written to TDR.

[4] Break output at the end of serial

transmission:

To output a break in serial

transmission, set DDR for the port

corresponding to the TxD pin to 1,

clear DR to 0, then clear the TE bit

in SCR to 0.

Figure 15.5 Sample Serial Transmission Flowchart

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