CHAPTER 10 SERIAL INTERFACE FUNCTION
User’s Manual U12688EJ4V0UM00
306
10.3.5 Transmission by CSI0 to CSI3
After changing the settings to enable transmission by clocked serial interface mode register n (CSIMn), writing to
the SIOn registers starts the transmit operation (n = 0 to 3).
(1) Starting the transmit operation
Starting the transmit operation is accomplished by setting the CTXEn bit of clocked serial interface mode
register n (CSIMn) (setting the CRXEn bit to 0), and writing transmit data to shift register n (SIOn).
Note that when the CTXEn bit = 0, the impedance of the SOn pin becomes high.
(2) Transmitting data in synchronization with the serial clock
(a) If the internal clock is selected as the serial clock
When transmission is started, the serial clock is output from the SCKn pin and at the same time, data
from the SIOn register is output sequentially to the SOn pin in synchronization with the fall of the serial
clock.
(b) If an external clock is selected as the serial clock
When transmission is started, data from the SIOn register is output sequentially to the SOn pin in
synchronization with the fall of the serial clock input to the SCKn pin after transmission starts. When
transmission is not started, the shift operation is not performed even if the serial clock is input to the SCKn
pin and the SOn pin’s output level does not change.
Figure 10-7. Timing of 3-Wire Serial I/O Mode (Transmission)
1
2
3
4
5
6
7
8
DO7 DO6 DO5 DO4 DO3 DO2 DO1 DO0
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
Содержание V850E/MS1 UPD703100
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