3-Wire Serial I/O Mode - NEC 78K0/KD1 Series User Manual

15.4.2 3-wire serial I/O mode

The 3-wire serial I/O mode is useful 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) Register setting
The 3-wire serial I/O mode is set by serial operation mode register 10 (CSIM10) and serial clock selection register
10 (CSIC10).
(a) Serial operation mode register 10 (CSIM10)
This register can be set by a 1-bit or 8-bit memory manipulation instruction.
RESET input clears this register to 00H.
Address: FF80H After reset: 00H R/W
Symbol 7
CSIM10 CSIE10
CSIE10
0
1
Note 2
TRMD10
Note 3
0
1
Note 4
DIR10
0
1
Note 5
CSOT10
0
1
Notes 1. Bit 0 is read-only.
2. Do not rewrite TRMD10 when CSOT10 = 1 (during serial communication).
3. The SO10 pin is fixed to the low level when TRMD10 is 0. Reception is started when data is read from
SIO10.
4. Do not rewrite DIR10 when CSOT10 = 1 (during serial communication).
5. CSOT10 is cleared if CSIE10 is set to 0 (operation stopped).
Caution Be sure to set bit 5 to 0.
316
CHAPTER 15 SERIAL INTERFACE CSI10
Note 1
6 5
TRMD10 0
Operation control in 3-wire serial I/O mode
Stops operation (SI10/P11/R D0, SO10/P12, and SCK10/P10/T
X
purpose port pins).
Enables operation (SI10/P11/R
Receive mode (transmission disabled)
Transmit/receive mode
MSB
LSB
Communication is stopped.
Communication is in progress.
Preliminary User's Manual U16315EJ1V0UD
4 3
DIR10 0
D0, SO10/P12, and SCK10/P10/T
X
Transmit/receive mode control
First bit specification
Operation mode flag
2 1 0
0 0 CSOT10
D0 pins can be used as general-
X
D0 pins are at active level).
X