upd70f3017ay Renesas Electronics Corporation., upd70f3017ay Datasheet - Page 227

• Manufacturer Part Number: upd70f3017ay
• Description: V850/sa1tm 32-/16-bit Single-chip Microcontroller
• Manufacturer: Renesas Electronics Corporation.

(b) Communication operations
(c) Transfer start
In 3-wire serial I/O mode, data is transmitted and received in 8-bit units. Each bit of data is transmitted or
received in synchronization with the serial clock.
Serial I/O shift register n (SIOn) is shifted in synchronization with the falling edge of the serial clock.
Transmission data is held in the SOn latch and is output from the SOn pin. Data that is received via the SIn
pin in synchronization with the rising edge of the serial clock is latched to SIOn.
Completion of an 8-bit transfer automatically stops operation of SIOn and sets the interrupt request flag
(INTCSIn).
A serial transfer starts when the following two conditions have been satisfied and transfer data has been set
to serial I/O shift register n (SIOn).
• The SIOn operation control bit (CSIEn) = 1
• After an 8-bit serial transfer, the internal serial clock is either stopped or is set to high level.
The transfer data is set to SIOn as follows.
• Transmit/receive mode
• Receive-only mode
Completion of an 8-bit transfer automatically stops the serial transfer operation and sets the interrupt request
flag (INTCSIn).
When CSIEn = 1 and MODEn = 0, transfer starts when writing to SIOn.
When CSIEn = 1 and MODEn = 1, transfer starts when reading from SIOn.
Caution After data has been written to SIOn, transfer will not start even if the CSIEn bit value is
Serial clock
set to “1”.
INTCSIn
SO0
SI0
Figure 10-4. Timing of 3-Wire Serial I/O Mode
CHAPTER 10 SERIAL INTERFACE FUNCTION
Transfer starts in synchronization with the serial clock’s falling edge
1
DO7 DO6 DO5 DO4 DO3 DO2 DO1
DI7
2
User’s Manual U12768EJ4V1UD
DI6
3
DI5
4
DI4
5
DI3
6
DI2
7
DI1
Transfer completion
8
DO0
DI0
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