uPD789074 Subseries 8-Bit Single-Chip Microcontrollers UD - Home

CHAPTER 9 SERIAL INTERFACE 20Figure 9-11. 3-Wire Serial I/O Mode Timing (7/7)(xii) Slave operation (when DAP20 = 1, CKP20 = 1, SSE20 = 1)SS20SIO20WriteSCK201 2 3 4 5 6 7 8SI20DI7 DI6 DI5 DI4 DI3 DI2 DI1 DI0SO20Hi-ZNote 1DO7 DO6 DO5 DO4 DO3 DO2 DO1 DO0 Note 2Hi-ZINTCSI20Notes 1. The value of the last bit previously output is output.2. DO0 is output until SS20 rises.When SS20 is high, SO20 is in a high-impedance state.(3) Transfer startSerial transfer is started by setting transfer data to the transmit shift register (TXS20/SIO20) when thefollowing two conditions are satisfied.• Serial operation mode register 20 (CSIM20) bit 7 (CSIE20) = 1• Internal serial clock is stopped or SCK20 is high after 8-bit serial transfer.Caution If CSIE20 is set to "1" after data is written to TXS20/SIO20, transfer does not start.The termination of 8-bit transfer stops the serial transfer automatically and generates the interrupt requestsignal (INTCSI20).User’s Manual U14801EJ3V1UD 149