H8SSLASH2225 datasheet(677/1071 Pages) RENESAS

677 / 1071 page

Section 15 Serial Communication Interface (SCI)

Rev. 5.00 Aug 08, 2006 page 591 of 982

REJ09B0054-0500

Figure 15.10 shows a sample flowchart for 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*

1 or

the DTC*

2 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 DR for the port

corresponding to the TxD pin to 0,

clear DDR to 1, then clear the TE

bit in SCR to 0.

Notes: 1. Supported only by the H8S/2239

Group.

2. The case, in which the DTC

automatically checks and 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 15.10 Sample Serial Transmission Flowchart

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