216
Bit 0: STF
Description
0
Read
Indicates that transfer is stopped
(initial value)
Write
Invalid
1
Read
Indicates transfer in progress
Write
Starts a transfer operation
Serial Data Register U (SDRU)
Bit
7
6
5
4
3
2
1
0
SDRU7
SDRU6
SDRU5
SDRU4
SDRU3
SDRU2
SDRU1
SDRU0
Initial value
Undefined Undefined Undefined Undefined Undefined Undefined Undefined Undefined
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. It is used as the data register for the upper 8 bits in 16-bit
transfer (SDRL is used for the lower 8 bits).
Data written to SDRU is output to SDRL starting from the least significant bit (LSB). This data is
then replaced by LSB-first data input at pin SI
1
, which is shifted in the direction from the most
significant bit (MSB) toward the LSB.
SDRU must be written or read only after data transmission or reception is complete. If this register
is written or read while a data transfer is in progress, the data contents are not guaranteed.
The SDRU value upon reset is not fixed.
Serial Data Register L (SDRL)
Bit
7
6
5
4
3
2
1
0
SDRL7
SDRL6
SDRL5
SDRL4
SDRL3
SDRL2
SDRL1
SDRL0
Initial value
Undefined Undefined Undefined Undefined Undefined Undefined Undefined Undefined
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
SDRL is an 8-bit read/write register. It is used as the data register in 8-bit transfer, and as the data
register for the lower 8 bits in 16-bit transfer (SDRU is used for the upper 8 bits).
In 8-bit transfer, data written to SDRL is output from pin SO
1
starting from the least significant bit
(LSB). This data is than replaced by LSB-first data input at pin SI
1
, which is shifted in the
direction from the most significant bit (MSB) toward the LSB.
In 16-bit transfer, operation is the same as for 8-bit transfer, except that input data is fed in via
SDRU.