402CHAPTER 18 SERIAL INTERFACE CHANNEL 1Start bit switching is realized by switching the bit order write to SIO1. The SIO1 shift order remains unchanged.Thus, switching between MSB-first and LSB-first must be performed before writing data to SIO1.(4) Transfer startSerial transfer is started by setting transfer data to the serial I/O shift register 1 (SIO1) when the following twoconditions are satisfied.• Serial interface channel 1 operation control bit (CSIE1) = 1• Internal serial clock is stopped or SCK1 is a high level after 8-bit serial transfer.Caution If CSIE1 is set to "1" after data write to SIO1, transfer does not start.Upon termination of 8-bit transfer, serial transfer automatically stops and the interrupt request flag (CSIIF1)is set.Figure 18-7. Circuit of Switching in Transfer Bit Order76Internal Bus10LSB-firstMSB-first Read/Write GateSI1 Serial I/O Shift Register 1 (SIO1)Read/Write GateSO1SCK1D QSO1 Latch
