UPD780828A Datasheet, PDF (216/472 Pages) NEC – 8-bit Single-Chip Microcontroller

Chapter 14 Serial Interface SIO31
(5) Transfer start
A serial transfer starts when the following conditions have been satisfied and transfer data has
been set to serial I/O shift register 31 (SIO31).
• The SIO31 operation control bit must be set (CSIE = 1)
• In Transmit/receive mode
When CSIE31 = 1 and MODE31 = 0, transfer starts when writing to SIO31.
• In Receive-only mode
When CSIE31 = 1 and MODE31 = 1, transfer starts when reading from SIO31.
Caution: After the data has been written to SIO31, the transfer will not start even if the CSIE31
bit value is set to “1”.
The completion of an 8-bit transfer automatically stops the serial transfer operation and sets a serial
transfer completion flag.
After an 8-bit serial transfer, the internal serial clock is either stopped or is set to high level.
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User’s Manual U16504EE1V1UD00