3-Wire Serial I/O Mode With Automatic Transmit/Receive Function - NEC PD789488 User Manual

12.4.3 3-wire serial I/O mode with automatic transmit/receive function

This 3-wire serial I/O mode is used for transmission/reception of a maximum of 16-byte data without the use of
software. Once transfer is started, the set number of bytes of data prestored in the RAM can be transmitted, and the
set number of bytes of data can be received and stored in the RAM.
(1) Register setting
The 3-wire serial I/O mode with automatic transmit/receive function is set with serial operation mode register
1A0 (CSIM1A0), automatic data transmit/receive control register 0 (ADTC0), automatic data transmit/receive
interval specification register 0 (ADTI0), 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 port mode register 2 (PM2) in the 3-wire serial I/O mode with automatic transmit/
receive function 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).
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CHAPTER 12 SERIAL INTERFACE 1A0
User's Manual U15331EJ4V1UD