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Transmitting Serial Data (Asynchronous Mode): Figure 11-5 shows a sample flowchart for
transmitting serial data and indicates the procedure to follow.
Start transmitting
Read TDRE flag in SSR
TDRE = 1?
Write transmit data
in TDR and clear TDRE
flag to 0 in SSR
All data
transmitted?
End
1
2
3
No
Yes
No
Yes
Read TEND flag in SSR
TEND = 1?
No
Yes
Output break
signal?
No
Yes
Clear TE bit to 0 in SCR
4
Clear DR bit to 0,
set DDR bit to 1
Initialize
1. SCI initialization: the transmit data output function
of the TxD pin is selected automatically. After the TE bit
is set to 1, one frame of 1s is output, then transmission is
possible.
2. SCI status check and transmit data write: read SSR,
check that the TDRE flag is 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.
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
(DDR and DR are I/O port registers), then clear the
TE bit to 0 in SCR.
Figure 11-5 Sample Flowchart for Transmitting Serial Data