430CHAPTER 18 SERIAL INTERFACE CHANNEL 1(4) Synchronization ControlBusy control and strobe control are functions for synchronizing sending and receiving between the masterdevice and slave device.By using these functions, it is possible to detect bit slippage during sending and receiving.(a) Busy control OptionBusy control is a function which causes the master device’s serial transmission to wait when the slavedevice outputs a busy signal to the master device, and maintain the wait state while that busy signal isactive.When the busy control option is used, the conditions shown below are necessary.• Bit 5 (ATE) of serial operation mode register 1 (CSIM1) should be set at (1).• Bit 1 (BUSY1) of the auto data send and receive control register (ADTC) should be set at (1).The system configuration between the master device and slave device in cases where the busy controloption is used is shown in Figure 18-18.Figure 18-18. System Configuration When the Busy Control Option is UsedThe master device inputs the busy signal output by the slave device to pin BUSY/P24. In sync with thefall of the serial clock, the master device samples the input busy signal. Even if the busy signal becomesactive during sending or receiving of 8 bit data, the wait does not apply. If the busy signal becomes activeat the rise of the serial clock 2 clock cycles after sending or receiving of 8 bit data ends, the busy inputfirst becomes effective at that point, and thereafter, sending or receiving of data waits during the periodthat the busy signal is active.The busy signal’s active level is set in bit 0 (BUSY0) of ADTC.BUSY0 = 0: Active HighBUSY0 = 1: Active LowSCK1SO1SI1SCK1SO1SI1BUSYMaster Device(μPD78054, 78054Y Sub-series) Slave Device
