3-Wire Serial I/O Mode Operation - NEC PD78076 User Manual

Pd78078 series; pd78078y series 8-bit single-chip microcontrollers

Table of Contents

19.4.2 3-wire serial I/O mode operation

The 3-wire serial I/O mode is valid for connection of peripheral I/O units and display controllers which incorporate

a conventional synchronous serial interface such as the 75X/XL, 78K, and 17K Series.

Communication is carried out with three lines of serial clock (SCK1), serial output (SO1) and serial input (SI1).

(1) Register setting

The 3-wire serial I/O mode is set with the 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.

CSIM1 CSIE1 DIR

Serial Interface Channel 1 Clock Selection

Clock externally input to SCK1 pin

8-bit timer register 2 (TM2) output

Clock specified with bits 4 to 7 of timer clock select register 3 (TCL3)

Serial Interface Channel 1 Operating Mode Selection

3-wire serial I/O mode

3-wire serial I/O mode with automatic transmit/receive function

P20 PM21 P21 PM22

Note 1 Note 1 Note 1 Note 1

Notes 1. If the 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 port function.

3. Can be used as P20 (CMOS input/output) when only transmitter is used (set bit 7 (RE) of ADTC

: Don't care

PMxx : Port mode register

: Port output latch

CHAPTER 19 SERIAL INTERFACE CHANNEL 1

CSIM11 CSIM10

Shift Register 1

SI1 Pin Function

Serial Clock Counter

Operation Control

input/output)

SO1 Pin Function

(CMOS output)

Pin Function

input/output)