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Chapter 11 Serial Interface 0, 1
XI - 26
Operation
Received Buffer Empty Flag
When the reception is completed (the last data reception edge of the clock is input), data is stored to
RXBUFn from the internal shift register, automatically. If data is stored to the shift register RXBUFn, the
received buffer empty flag SCnREMP of the SCnMD3 register is set to "1". That indicates that the
received data is going to be read. SCnREMP is cleared to "0" by reading out the data of RXBUFn.
Transmission Buffer Empty Flag
If any data is set to TXBUFn again, during communication (after setting data to TXBUFn before generat-
ing the communication complete interrupt SCnIRQ), the transmission buffer empty flag SCnTEMP of the
SCnMD3 register is set to "1". That indicates that the next transmission data is going to load. Data is
loaded to the inside shift register from TXBUFn by generation of SCnTIRQ, and the next transfer is
started as SCnTEMP is cleared to "0".
Overrun Error and Error Monitor Flag
If, after reception complete, the next data has been already received before reading out the data of the
received data buffer RXBUFn, overrun error is generated and the SCnORE flag of the SCnMD3 register
is set to "1". And at the same time, the error monitor flag SCnERE is set to indicate that something wrong
on reception. The SCnORE flag holds the status unless the data of RXBUFn is read out. SCnERE is
cleared as SCnORE flag is cleared. These error flags are nothing to do with communication operation.
Reception BUSY Flag
When any data is set to TXBUFn or when the SCnSBIS flag of the SCnMD1 register is "1" as start
condition is input, the SCnRBSY flag of the SCnMD3 register is set to "1". And, on the generation of the
communication complete interrupt SCnTIRQ, the flag is cleared to "0". And, during continuous commu-
nication, the SCnRBSY falg is always set. If the transmission buffer empty flag SCnTEMP is cleared to
"0" as the communication complete interrupt SCnTIRQ is generated, SCnRBSY is cleared to "0". If the
SCnSBIS flag is set to "0" during communication, the SCnRBSY flag is cleared to "0".
Transmission BUSY Flag
When any data is set to TXBUFn or when the SCnSBOS flag of the SCnMD1 register is "1" as start
condition is input, the SCnTBSY flag of the SCnMD3 register is set to "1". And, on the generation of the
communication complete interrupt SCnTIRQ, the flag is cleared to "0". And, during continuous commu-
nication, the SCnTBSY flag is always set. If the transmission buffer empty flag SCnTEMP is cleared to
"0" as the communication complete interrupt SCnTIRQ is generated, SCnTBSY is cleared to "0". If the
SCnSBOS flag is set to "0" during communication, the SCnTBSY flag is cleared to "0".