Wire Serial I/O Mode Timing - NEC mPD780208 Subseries User Manual

(2) Communication operation
The 3-wire serial I/O mode is used for data transmission/reception in 8-bit units. Data transmission/
reception is carried out bit by bit in synchronization with the serial clock.
Shift operations of serial I/O shift register 0 (SIO0) are carried out at the falling edge of the serial clock
(SCK0). The transmit data is held in the SO0 latch and is output from the SO0 pin. The receive data
input to the SI0 pin is latched into SIO0 at the rising edge of SCK0.
Upon termination of 8-bit transfer, SIO0 operation stops automatically and the interrupt request flag
(CSIIF0) is set.
SCK0
SI0
SO0
CSIIF0
The SO0 pin is used for CMOS output and generates the SO0 latch status. Thus, the SO0 pin output
status can be manipulated by setting bit 0 (RELT) and bit 1 (CMDT) of the serial bus interface control
register (SBIC).
However, do not carry out this manipulation during serial transfer.
Control the SCK0 pin output level in the output mode (internal system clock mode) by manipulating the
P27 output latch (refer to 13.4.5 SCK0/P27 pin output manipulation).
CHAPTER 13 SERIAL INTERFACE CHANNEL 0
Figure 13-6. 3-Wire Serial I/O Mode Timing
1 2 3
DI7 DI6 DI5
DO7 DO6 DO5
Transfer start at falling edge of SCK0
User's Manual U11302EJ4V0UM
4 5 6
DI4 DI3 DI2
DO4 DO3 DO2
7 8
DI1 DI0
DO1 DO0
End of transfer
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