H83318 Datasheet, PDF (341/574 Pages) Renesas Technology Corp – Single-Chip Microcomputer

14.2.4 Transmit Data Register (TDR)
Bit
7
6
5
4
3
2
1
0
Initial value
Read/Write
1
1
1
1
1
1
1
1
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
TDR is an 8-bit readable/writable register that holds the next data to be transmitted. When TSR
becomes empty, the data written in TDR is transferred to TSR. Continuous data transmission is
possible by writing the next data in TDR while the current data is being transmitted from TSR.
TDR is initialized to H'FF by a reset and in the standby modes.
14.2.5 Serial Mode Register (SMR)
Bit
Initial value
Read/Write
7
6
5
C/A
CHR
PE
0
0
0
R/W
R/W
R/W
4
3
2
1
0
O/E STOP
MP
CKS1 CKS0
0
0
0
0
0
R/W
R/W
R/W
R/W
R/W
SMR is an 8-bit readable/writable register that controls the communication format and selects the
clock source of the on-chip baud rate generator. It is initialized to H'00 by a reset and in the
standby modes. For further information on the SMR settings and communication formats, see
tables 14.5 and 14.7 in section 14.3, Operation.
Bit 7—Communication Mode (C/A): This bit selects asynchronous or synchronous
communication mode.
Bit 7
C/A
0
1
Description
Asynchronous communication
Synchronous communication
(Initial value)
Bit 6—Character Length (CHR): This bit selects the character length in asynchronous mode.
It is ignored in synchronous mode.
Bit 6
CHR
0
1
Description
8 bits per character
(Initial value)
7 bits per character (Bits 0 to 6 of TDR and RDR are used for transmitting and
receiving, respectively)
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