10.2.4 Transmit data register (TDR)
TDR is an 8-bit register that stores transmit data. When TSR is found to be empty, the transmit data
written in TDR is transferred to TSR, and serial data transmission is started. Continuous
transmission is possible by writing the next transmit data to TDR during TSR serial data
transmission.
TDR can be read or written by the CPU at any time.
TDR is initialized to H'FF upon reset, and in standby, module standby, or watch mode.
10.2.5 Serial mode register (SMR)
SMR is an 8-bit register used to set the serial data transfer format and to select the clock source for
the baud rate generator.
SMR can be read or written by the CPU at any time.
SMR is initialized to H'00 upon reset, and in standby, module standby, or watch mode.
Bit 7: Communication mode (COM)
Bit 7 selects whether SCI3 operates in asynchronous mode or synchronous mode.
Bit 7
COM
Description
0
Asynchronous mode
(initial value)
1
Synchronous mode
Bit
Initial value
Read/Write
7
COM
0
R/W
6
CHR
0
R/W
5
PE
0
R/W
4
PM
0
R/W
3
STOP
0
R/W
0
CKS0
0
R/W
2
MP
0
R/W
1
CKS1
0
R/W
Bit
Initial value
Read/Write
7
TDR7
1
R/W
6
TDR6
1
R/W
5
TDR5
1
R/W
4
TDR4
1
R/W
3
TDR3
1
R/W
0
TDR0
1
R/W
2
TDR2
1
R/W
1
TDR1
1
R/W
254