Datasheet

Section 15 Serial Communication Interface (SCI)
Rev. 6.00 Mar. 18, 2010 Page 604 of 982
REJ09B0054-0600
3. 8-bit data is sent from the TxD pin synchronized with the output clock when output clock
mode has been specified, and synchronized with the input clock when use of an external clock
has been specified.
4. The SCI checks the TDRE flag at the timing for sending the MSB (bit 7).
5. If the TDRE flag is cleared to 0, data is transferred from TDR to TSR, and serial transmission
of the next frame is started.
6. If the TDRE flag is set to 1, the TEND flag in SSR is set to 1, and the TDRE flag maintains the
output state of the last bit. If the TEIE bit in SCR is set to 1 at this time, a TEI interrupt request
is generated. The SCK pin is fixed high.
Figure 15.20 shows a sample flow chart for serial data transmission. Even if the TDRE flag is
cleared to 0, transmission will not start while a receive error flag (ORER, FER, or PER) is set to 1.
Make sure that the receive error flags are cleared to 0 before starting transmission. Note that
clearing the RE bit to 0 does not clear the receive error flags.
Transfer direction
Bit 0
Serial data
Synchronization
clock
1 frame
TDRE
TEND
Data written to TDR
and TDRE flag cleared
to 0 in TXI interrupt
service routine
TXI interrupt
request generated
Bit 1 Bit 7 Bit 0 Bit 1 Bit 6 Bit 7
TXI interrupt
request generated
TEI interrupt request
generated
Figure 15.19 Sample SCI Transmission Operation in Clocked Synchronous Mode