CHAPTER 14 SERIAL INTERFACE CHANNEL 1269User’s Manual U11302EJ4V0UM14.4.2 3-wire serial I/O mode operationThe 3-wire serial I/O mode is used for connection of peripheral ICs and display controllers that incorporatea clocked serial interface.Communication is carried out using three lines: a serial clock (SCK1), serial output (SO1), and serial input(SI1).(1) Register settingThe 3-wire serial I/O mode is set by serial operating mode register 1 (CSIM1).CSIM1 is set with a 1-bit or 8-bit memory manipulation instruction.RESET input sets CSIM1 to 00H.CSIM CSIM Serial interface channel 1 clock selection11 100 x Clock externally input to SCK1 pinNote 11 0 8-bit timer register 2 (TM2) output1 1 Clock specified with bits 4 to 7 of timer clock select register 3 (TCL3)ATE Serial interface channel 1 operating mode selection0 3-wire serial I/O mode1 3-wire serial I/O mode with automatic transmit/receive functionDIR Start bit SI1 pin function SO1 pin function0 MSB SI1/P20 (input) SO1 (CMOS output)1 LSBCSIM Shift register Serial clock counter SI1/P20 SO1/P21 SCK1/P22CSIE1 PM20 P20 PM21 P21 PM22 P2211 1 operation operation control pin function pin function pin functionNote 2 Note 2 Note 2 Note 2 Note 2 Note 2 Operation stop Clear P20 P21 P220 × × × × × × × (CMOS I/O) (CMOS I/O) (CMOS I/O)Operation enable Count operation SI1Note 3 SO1 SCK10 1 ×Note 3 Note 3 (input) (CMOS output) (input)1 1 × 0 0SCK11 0 1 (CMOS output)Notes 1. If external clock input has been selected with CSIM11 set to 0, set bit 1 (BUSY1) and bit 2 (STRB)of the automatic data transmit/receive control register (ADTC) to 0, 0.2. Can be used freely as a port pin.3. Can be used as P20 when used only for transmission (set bit 7 (RE) of ADTC to 0).Remark ×: don’t carePM××: Port mode registerP××: Port output latchCSIE1 DIR ATE 0 0 0 CSIM11CSIM10<7> 6 <5> 4 3 2 1 0CSIM1SymbolFF68H 00H R/WAddress After reset R/W
