CHAPTER 10 SERIAL INTERFACE FUNCTION
User’s Manual U12688EJ4V0UM00
307
10.3.6 Reception by CSI0 to CSI3
When the reception disabled setting is changed to reception enabled for clocked serial interface mode register n
(CSIMn), and data is read from the SIOn register in the reception enabled state, a receive operation is started (n = 0
to 3).
(1) Starting the receive operation
The following 2 methods can be used to start receive operations.
<1> If the CRXEn bit of the CSIMn register is changed from the reception disabled state (0) to the reception
enabled state (1)
<2> If the CRXEn bit of the CSIMn register reads receive data from shift register n (SIOn) when in the
reception enabled state (1)
When the CRXEn bit of the CSIMn register is set (1), even if 1 is written again, a receive operation is not
started. Note that when the CRXEn bit = 0, the shift register input becomes 0.
(2) Receiving data in synchronization with the serial clock
(a) If the internal clock is selected as the serial clock
When reception is started, the serial clock is output from the SCKn pin and at the same time, data from
the SIn pin is fetched sequentially to the SIOn register in synchronization with the rise of the serial clock.
(b) If an external clock is selected as the serial clock
When reception is started, data from the SIn pin is fetched sequentially to the SIOn register in
synchronization with the rise of the serial clock input to the SCKn pin after reception starts. When
reception has not started, the shift operation is not performed even if the serial clock is input to the SCKn
pin.
Figure 10-8. Timing of 3-Wire Serial I/O Mode (Reception)
1
2
3
4
5
6
7
8
DI7 DI6 DI5 DI4 DI3 DI2 DI1 DI0
SCKn
SIn
SOn
Serial transmission/reception complete
interrupt generation
Transfer start in synchronization with falling of SCKn
Execution of write instruction to SIOn register
INTCSIn interrupt
Remark
n = 0 to 3
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