3-Wire Serial I/O Mode - NEC 78K0 User Manual

14.4.2 3-wire serial I/O mode

The 3-wire serial I/O mode is used for connecting peripheral ICs and display controllers that have a clocked serial
interface.
In this mode, communication is executed by using three lines: the serial clock (SCK10), serial output (SO10), and
serial input (SI10) lines.
(1) Registers used
• Serial operation mode register 10 (CSIM10)
• Serial clock selection register 10 (CSIC10)
• Port mode register 1 (PM1)
• Port register 1 (P1)
The basic procedure of setting an operation in the 3-wire serial I/O mode is as follows.
<1> Set the CSIC10 register (see Figure 14-3).
<2> Set bits 0, 4, and 6 (CSOT10, DIR10, and TRMD10) of the CSIM10 register (see Figure 14-2).
<3> Set bit 7 (CSIE10) of the CSIM10 register to 1. → Transmission/reception is enabled.
<4> Write data to transmit buffer register 10 (SOTB10). → Data transmission/reception is started.
Read data from serial I/O shift register 10 (SIO10). → Data reception is started.
Caution Take relationship with the other party of communication when setting the port mode
register and port register.
CHAPTER 14 SERIAL INTERFACE CSI10
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