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

16.4.2 3-wire serial I/O mode

The 3-wire serial I/O mode is used for connecting peripheral ICs and display controllers with a clocked serial
interface.
In this mode, communication is executed by using three lines: the serial clock (SCK1n), serial output (SO1n), and
serial input (SI1n) lines.
(1) Registers used
• Serial operation mode register 1n (CSIM1n)
• Serial clock selection register 1n (CSIC1n)
• Port mode register 0 (PM0) or port mode register 1 (PM1)
• Port register 0 (P0) or 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 CSIC1n register (see Figures 16-5 and 16-6).
<2> Set bits 0 and 4 to 6 (CSOT1n, DIR1n, SSE11 (serial interface CSI11 only), and TRMD1n) of the CSIM1n
register (see Figures 16-3 and 16-4).
<3> Set bit 7 (CSIE1n) of the CSIM1n register to 1. → Transmission/reception is enabled.
<4> Write data to transmit buffer register 1n (SOTB1n). → Data transmission/reception is started.
Read data from serial I/O shift register 1n (SIO1n). → Data reception is started.
Caution Take relationship with the other party of communication when setting the port mode
register and port register.
Remark n = 0:
n = 0, 1:
368
CHAPTER 16 SERIAL INTERFACES CSI10 AND CSI11
µ
PD780143, 780144
µ
PD780146, 780148, 78F0148
User's Manual U15947EJ2V0UD
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