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Chapter 11 Serial Interface 0, 1
XI - 22
Operation
Start Condition Setup
The SCnSTE flag of the SCnMD0 register sets if a start condition is enabled or not. If a start condition is
enabled, and received at communication, a bit counter is cleared to restart the communication. The start
condition, if the SCnCE1 flag of the SCnMD0 register is set to "0", is regarded when a data line (SBI pin
(with 3 channels) or SBO pin (with 2 channels) is changed from "H" to "L" as a clock line (SBT pin) is "H".
Also, the start condition, if the SCnCE1 flag of the SCnMD0 register is set to "1", is regarded when a
data line (SBI pin (with 3 channels) or SBO pin (with 2 channels) is changed from "H" to "L" as a clock line
(SBT pin) is "L". Both the SCnSBOS flag and the SCnSBIS flag of the SCnMD1 register should be set to
"0", before the start condition setup is changed
First Transfer Bit Setup
The SCnDIR flag of the SCnMD0 register can set the first transfer bit. MSB first or LSB first can be
selected.
Transmission Data Buffer
The transmission data buffer, TXBUFn is the sub buffer that stores data to load the internal shift register.
Data to be transfered should be set to the transmission data buffer, TXBUFn to load to the internal shift
register automatically. The first data loading to the internal shift register is done at the same timing of the
data setting to TXBUFn.
Received Data Buffer
The received data buffer RXBUFn is the sub buffer that pushed the received data in the internal shift
register. After the communication complete interrupt SCnIRQ is generated, data stored in the internal
shift register is stored to the received data buffer RXBUFn automatically. RXBUFn can store data up to
1 byte. RXBUFn is rewritten in every communication complete, so read out data of RXBUFn till the next
receive complete. The received data buffer empty flag SCnREMP is set to "1" at the same time
SCnTIRQ is generated. SCnREMP is cleared to "0" after RXBUFn is read.
Start condition should be switched after both the SCnSBOS and the SCnSBIS flags of the
SCnMD1 register are set to "0". If they are not set to "0", the switching is not valid.
If a start condition is input to restart during communication, the transmission data is not valid.
If the transmission should be operated again, set the transmission data to TXBUFn, again.
RXBUFn is rewritten in every communication complete. At continuous communication, data
of RXBUFn should be read out till the next reception complete.