357CHAPTER 17 SERIAL INTERFACE CHANNEL 0 (μPD78078 SUBSERIES)(d) For pins which are to be used for data input/output, be sure to carry out the following settings beforeserial transfer of the 1st byte after RESET input.<1> Set 1 to the output latch of P25 and P26<2> Set 1 to bit 0 (RELT) of the serial bus interface control register (SBIC).<3> Set 0 to the output latch of P25 and P26, to which 1 has been set.(e) If the SB0 (SB1) line changes from low level to high level or from high level to low level while the SCK0line is at high level, it is recognized as either a bus release signal or a command signal. Therefore,if the changing timing of bus fluctuates because of the wiring capacitance, etc., this may be wronglyinterpreted as a bus release signal (or a command signal) even while data is being transmitted. Careshould be taken in the wiring.17.4.4 2-wire serial I/O mode operationThe 2-wire serial I/O mode can cope with any communication format by program.Communication is basically carried out with two lines of serial clock (SCK0) and serial data input/output (SB0or SB1).Figure 17-31. Serial Bus Configuration Example Using 2-Wire Serial I/O ModeMasterSCK0SlaveSB0 (SB1)SCK0SB0 (SB1)VDDVDD
