R01UH0823EJ0100 Rev.1.00
Page 1028 of 1823
Jul 31, 2019
RX23W Group
33. Serial Communications Interface (SCIg, SCIh)
Figure 33.13
Example of Serial Transmission Flowchart in Asynchronous Mode
Initialization
Start data transmission
[ 1 ]
[ 2 ]
No
End
Yes
Write transmit data to TDR
No
Yes
No
Yes
No
Yes
Set the I/O port functions
Set bits SCR.TIE, TE, and TEIE to 0
TXI interrupt
All transmit data written?
TEI interrupt
Break output
[ 4 ]
[ 3 ]
Set the SCR.TIE bit to 0 and set the
SCR.TEIE bit to 1
Note:
The TDR register becomes the TDRH and TDRL registers
when 9-bit data length is selected. Write data in the order from
TDRH to TDRL.
[ 1 ]
SCI initialization:
Set data transmission.
After the TE bit in SCR is set to 1, high is output for a frame,
and transmission is enabled.
[ 2 ]
Transmit data write to TDR by a TXI interrupt request:
When transmit data is transferred from TDR to TSR, a transmit
data empty interrupt (TXI) request is generated.
Write transmit data to TDR once in the TXI interrupt handling
routine.
[ 3 ]
Serial transmission continuation procedure:
To continue serial transmission, write transmit data to TDR
once using a TXI interrupt request.
Transmit data can also be written to TDR by activating the
DMAC or DTC.
When TEI interrupt requests are in use, set the SCR.TIE bit to 0
and the SCR.TEIE bit to 1 after the last of the data to be
transmitted are written to the TDR
[ 4 ]
Break output at the end of serial transmission:
To output a break in serial transmission, set the I/O port
function corresponding to the TXDn pin (corresponding to
output of the low level), and after switching the TXDn pin to the
general I/O port function, set the TE bit in the SCR to 0.