HD6433832S Datasheet, PDF (245/560 Pages) Renesas Technology Corp – single-chip microcomputers

Bits 4 to 2—Reserved Bits: Bits 4 to 2 are reserved; they are always read as 0, and cannot be
modified.
Bit 1—Reserved Bit: Bit 1 is reserved; it should always be cleared to 0.
Bit 0—Start Flag (STF): Bit 0 controls the start of a transfer. Setting this bit to 1 causes SCI1 to
start transferring data.
During the transfer or while waiting for the first clock pulse, this bit remains set to 1. It is cleared
to 0 upon completion of the transfer. It can therefore be used as a busy flag.
Bit 0: STF
0
1
Description
Read: Indicates that transfer is stopped
Write: Invalid
Read: Indicates transfer in progress
Write: Starts a transfer operation
(initial value)
Serial Data Register U (SDRU)
Bit
Initial value
Read/Write
7
6
5
4
3
2
1
0
SDRU7 SDRU6 SDRU5 SDRU4 SDRU3 SDRU2 SDRU1 SDRU0
Not fixed Not fixed Not fixed Not fixed Not fixed Not fixed Not fixed Not fixed
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 SI₁, 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.
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