
353
14.7 Operation of the Operation Mode 0
Figure 14.7-3 Transfer Data Format
I
Receiving Operation in CLK Asynchronous Mode
Select the baud rate clock with bits CLK2 to CLK0 in the SMC2 register. For the baud rate
clock, see Figure 14.7-1 "Baud Rate Calculation Expression for Internal and External Clocks"
and Figure 14.7-2 "Baud Rate Calculation Expression when the Dedicated Baud Rate
Generator is Used". In a receiving operation, reception is permitted when the RXE bit in the
SMC1 register is "1" and the receiving operation starts at the first falling edge of the input data
(detection of the start bit). When the receiving operation is completed, the RDRF bit in the SSD
register is set to "1" and the received data is loaded to the SIDR register. If the RDRF bit is set
to "1" when the RIE bit is "1," a reception interrupt to the CPU is generated. If any of the three
errors (PER/OVE/FER) is detected when reception is completed, the RDRF bit is not set to "1"
and the received data is not loaded to the SIDR register. Therefore, the value in the SIDR
register is the previously received data. Unless the RXE bit is set to "0," the receiving operation
is continued whenever a start bit is detected even if an error flag is set.
Figure 14.7-4 Receiving Operation of CLK Asynchronous Mode
If "0" is written to the RXE bit of the SMC2 register during a receiving operation, the receiving
operation is prohibited after data reception is completed.
St
D0
D1
D2
D3
D4
D5
D6
Sp
Sp
7-bit length
No parity
Stop bits: 2 bits
St
D0
D1
D2
D3
D4
D5
D6
Sp
Sp
7-bit length
With parity
Stop bits: 2 bits
P
St
D0
D1
D2
D3
D4
D5
D6
Sp
Sp
8-bit length
No parity
Stop bits: 2 bits
D7
St
D0
D1
D2
D3
D4
D5
D6
Sp
Sp
8-bit length
With parity
Stop bits: 2 bits
D7
P
St
D0 to D7 : Data bit
P
Sp
: Start bit
: Parity bit
: Stop bit
SI
St
D0
D1
D2
D3
D4
D5
D6
Sp
Sp
D7
St
D0
D1
D2
RXE
Load to
SIDR
RDRF