Transmitting and Receiving Data
SCI Initialization: The SCI must be initialized in the same way as in asynchronous mode. See
figure 12.4. When switching from asynchronous mode to synchronous mode, check that the
ORER, FER, and PER bits are cleared to 0. Transmitting and receiving cannot begin if ORER,
FER, or PER is set to 1.
Transmitting Serial Data: Follow the procedure in figure 12.13 for transmitting serial data.
1.
2.
SCI initialization: the transmit data output function
of the TxD pin is selected automatically.
1
2
Initialize
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.
Transition of the TDRE bit from 0 to 1 can be
reported by a TXI interrupt.
Start transmitting
Read TDRE bit in SSR
No
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.
TDRE = 1?
Yes
(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.
Write transmit data in
TDR and clear TDRE bit to
0 in SSR
Serial transmission
End of
transmission?
No
3
Yes
Read TEND bit in SSR
No
TEND = 1?
Yes
Clear TE bit to 0 in SCR
End
Figure 12.13 Sample Flowchart for Serial Transmitting
273
RENESAS [ RENESAS TECHNOLOGY CORP ]
