Transmitting Serial Data: Follow the procedure in figure 12.5 for transmitting serial data.
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.
1
Initialize
Start transmitting
2.
SCI status check and transmit data write: read
the serial status register (SSR), check that the
TDRE bit is 1, then write transmit data in the
transmit data register (TDR) and clear TDRE to 0.
If a multiprocessor format is selected, after
writing the transmit data write 0 or 1 in the
multiprocessor bit transfer (MPBT) in SSR.
Transition of the TDRE bit from 0 to 1 can be
reported by an interrupt.
2
Read TDRE bit in SSR
TDRE = 1?
No
Yes
Write transmit data in TDR
3. (a) To continue transmitting serial data: read the
TDRE bit to check whether it is safe to write; if
TDRE = 1, write data in TDR, then clear TDRE
to 0.
If using multiprocessor format,
select MPBT value in SSR
Clear TDRE bit to 0
Serial transmission
(b) To end serial transmission: end of transmission
can be confirmed by checking transition of the
TEND bit from 0 to 1. This can be reported by
a TEI interrupt.
End of
transmission?
No
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 TE to 0 in SCR.
3
Yes
Read TEND bit in SSR
No
No
TEND = 1?
Yes
Output break
signal?
4
Yes
Set DR = 0, DDR = 1
Clear TE bit in SCR to 0
End
Figure 12.5 Sample Flowchart for Transmitting Serial Data
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RENESAS [ RENESAS TECHNOLOGY CORP ]
