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Section 13 Serial Communication Interface
• Transmitting Serial Data (Asynchronous Mode): Figure 13.5 shows a sample flowchart for
transmitting serial data and indicates the procedure to follow.
Initialize
Start transmitting
Read TDRE flag in SSR
TDRE = 1
Yes
Write transmit data in TDR
and clear TDRE flag to 0 in SSR
All data transmitted?
Read TEND flag in SSR
TEND = 1
Yes
Output break signal?
Yes
Clear DR bit to 0 and set
DDR bit to 1
Clear TE bit to 0 in SCR
<End>
Figure 13.5 Sample Flowchart for Transmitting Serial Data
Rev. 4.00 Jan 26, 2006 page 514 of 938
REJ09B0276-0400
(1)
(2)
No
No
Yes
(3)
No
No
(4)
(1)
SCI initialization:
the transmit data output function of the TxD pin is
selected automatically.
(2)
SCI status check and transmit data write:
read SSR and check that the TDRE flag is set to 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. When the DMAC is activated by a
transmit-data-empty interrupt request (TXI) to write
data in TDR, the TDRE flag is checked and cleared
automatically.
(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, then
clear the TE bit to 0 in SCR.
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