H8S2245 datasheet(498/818 Pages) RENESAS

498 / 818 page

Section 12 Serial Communication Interface (SCI)

Rev.3.00 Mar. 26, 2007 Page 456 of 772

REJ09B0355-0300

Serial data transmission (clocked synchronous mode): Figure 12.16 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]

Clear TE bit in SCR to 0

TDRE = 1?

All data transmitted?

TEND = 1?

[1] SCI initialization:

The TxD pin is automatically

designated as the transmit data output

pin.

[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, be

sure to 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.

Note: * The case, in which the DTC

automatically clears the TDRE

flag, occurs only when DISEL in

DTC is 0 with the transfer

counter not being 0. Therefore,

the TDRE flag should be cleared

by CPU when DISEL is 1, or

when DISEL is 0 with the

transfer counter being 0.

Figure 12.16 Sample Serial Transmission Flowchart

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