NEC 78014Y Series, User Manual

Page: 281 / 547

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CHAPTER 15 SERIAL INTERFACE CHANNEL 0 (
µ
PD78014 Subseries)
281
(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-wise in synchronization of the serial clock.
Shift operation of the serial I/O shift register 0 (SIO0) is carried out at the falling edge of the serial clock (SCK0).
The transmitted data is held in the SO0 latch and is output from the SO0 pin. The received data input to the
SI0 pin is latched in 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.
Figure 15-8. 3-Wire Serial I/O Mode Timings
The SO0 pin serves 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.
The SCK0 pin output level is controlled by manipulating the P27 output latch in the output mode (internal system
clock mode) (refer to 15.4.5 SCK0/P27 pin output manipulation).
SCK0 1 2 3 4 5 6 7 8
SI0 DI7 DI6 DI5 DI4 DI3 DI2 DI1 DI0
SO0
DO7 DO6 DO5 DO4 DO3 DO2 DO1 DO0
CSIIF0
Transfer Start at the falling edge of SCK0
End of Transfer