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10.2.5
Serial mode register (SMR)
Bit
COM
Initial value
Read/Write
R/W
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
1
Synchronous mode
Bit 6: Character length (CHR)
Bit 6 selects either 7 or 8 bits as the data length to be used in asynchronous mode. In synchronous
mode the data length is always 8 bits, irrespective of the bit 6 setting.
Bit 6
CHR
Description
0
8-bit data/5-bit data
1
7-bit data
Notes: 1. When 7-bit data is selected, the MSB (bit 7) of TDR is not transmitted.
2. When 5-bit data is selected, set both PE and MP to 1. The three most significant bits
(bits 7, 6, and 5) of TDR are not transmitted.
7
6
5
CHR
PE
0
0
0
R/W
R/W
*2
*1
*2
/5-bit data
4
3
PM
STOP
MP
0
0
R/W
R/W
R/W
2
1
0
CKS1
CKS0
0
0
0
R/W
R/W
(initial value)
(initial value)
253
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