NEC 78K0 User Manual page 307

(2) Communication operation
In the 3-wire serial I/O mode, data is transmitted or received in 8-bit units. Each bit of the data is transmitted or
received in synchronization with the serial clock.
Data can be transmitted or received if bit 6 (TRMD10) of serial operation mode register 10 (CSIM10) is 1.
Transmission/reception is started when a value is written to transmit buffer register 10 (SOTB10). In addition,
data can be received when bit 6 (TRMD10) of serial operation mode register 10 (CSIM10) is 0.
Reception is started when data is read from serial I/O shift register 10 (SIO10).
After communication has been started, bit 0 (CSOT10) of CSIM10 is set to 1. When communication of 8-bit data
has been completed, a communication completion interrupt request flag (CSIIF10) is set, and CSOT10 is cleared
to 0. Then the next communication is enabled.
Caution Do not access the control register and data register when CSOT10 = 1 (during serial
communication).
(1) Transmission/reception timing (Type 1; TRMD10 = 1, DIR10 = 0, CKP10 = 0, DAP10 = 0)
SCK10
Read/write trigger
SOTB10
SIO10
CSOT10
INTCSI10
CSIIF10
SI10 (receive AAH)
SO10
55H is written to SOTB10.
CHAPTER 14 SERIAL INTERFACE CSI10
Figure 14-5. Timing in 3-Wire Serial I/O Mode (1/2)
55H (communication data)
ABH 56H
User's Manual U16227EJ2V0UD
ADH 5AH B5H 6AH D5H AAH
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