HD6432351 datasheet(614/1025 Pages) RENESAS

614 / 1025 page

Section 13 Serial Communication Interface (SCI)

Rev. 3.00 Sep 15, 2006 page 580 of 988

REJ09B0330-0300

Serial data transmission (asynchronous mode): Figure 13.5 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, a 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 DMAC or 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 13.5 Sample Serial Transmission Flowchart

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