Bit 1: Tail mark transmission flag (MTRF)
When MRKON = 1, bit 1 indicates that a tail mark is being transmitted. MTRF is a read-only bit,
and cannot be modified.
Bit 1
MTRF
Description
0
1
Idle state, or 8-bit/16-bit data transfer in progress
Tail mark transmission in progress
(initial value)
Bit 0: Start flag (STF)
The STF bit controls the start of transfer operations. SCI1 transfer operation is started when this
bit is set to 1.
STF remains set to 1 during transfer and while SCI1 is waiting for a start bit, and is cleared to 0
when transfer ends. It can therefore be used as a busy flag.
Bit 0
STF
Description
0
Read
Write
Read
Write
Transfer operation stopped
(initial value)
Invalid
1
Transfer operation in progress
Starts transfer operation
3. Serial data register U (SDRU)
Bit
7
6
5
4
3
2
1
0
SDRU7 SDRU6 SDRU5 SDRU4 SDRU3 SDRU2 SDRU1 SDRU0
Undefined Undefined Undefined Undefined Undefined Undefined Undefined Undefined
Initial value
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
SDRU is an 8-bit read/write register used as the data register for the upper 8 bits in 16-bit transfer
(while SDRL is used for the lower 8 bits).
The data written into SDRU is output to SDRL in LSB-first order. In the replacement process, data
is input LSB-first from the SI1 pin, and the data is shifted in the MSB → LSB direction.
SDRU read/write operations must only be performed after data transmission/reception has been
completed. Data contents are not guaranteed if read/write operations are executed while data
transmission/reception is in progress.
The value of SDRU is undefined upon reset.
258
ETC [ ETC ]
