NEC PD78F9488 - Manual (Page 225)

CHAPTER 12 SERIAL INTERFACE 1A0
User’s Manual U15331EJ4V1UD
225
12.4.2 3-wire serial I/O mode
The 3-wire serial I/O mode is useful for connection of peripheral I/Os and display controllers, etc., which
incorporate a conventional clocked serial interface, such as the 75XL Series, 78K Series, and 17K Series.
Communication is performed using three lines: a serial clock (SCK10), serial output (SO10), and serial input
(SI10).
(1) Register
setting
3-wire serial I/O mode settings are performed using serial operation mode register 1A0 (CSIM1A0), port
mode register 2 (PM2), and port 2 (P2).
(a) Serial operation mode register 1A0 (CSIM1A0)
CSIM1A0 is set with a 1-bit or 8-bit memory manipulation instruction.
RESET input sets CSIM1A0 to 00H.
Caution Set the port mode register 2 (PM2) in the 3-wire serial I/O mode as follows.
• In the case of serial clock output (master transmission or master reception)
Set the SCK10/P23 pin to output mode (PM23 = 0) and clear the output latch of P23 to 0.
• In the case of serial clock input (slave transmission or slave reception)
Set the SCK10/P23 pin to input mode (PM23 = 1).
• In transmission or transmission/reception mode
Set the SO10/P24 pin to output mode (PM24 = 0) and clear the output latch of P24 to 0.
Set the SI10/P25 pin to input mode (PM25 = 1).
• In reception mode
Set the SI10/P25 pin to input mode (PM25 = 1).