NEC 78K0 Series User Manual page 401

(3) Timing of output to SO1n pin (first bit)
When communication is started, the value of transmit buffer register 1n (SOTB1n) is output from the SO1n pin.
The output operation of the first bit at this time is described below.
Writing to SOTB1n or
reading from SIO1n
Output latch
Writing to SOTB1n or
reading from SIO1n
Output latch
The first bit is directly latched by the SOTB1n register to the output latch at the falling (or rising) edge of SCK1n,
and output from the SO1n pin via an output selector. Then, the value of the SOTB1n register is transferred to the
SIO1n register at the next rising (or falling) edge of SCK1n, and shifted one bit. At the same time, the first bit of
the receive data is stored in the SIO1n register via the SI1n pin.
The second and subsequent bits are latched by the SIO1n register to the output latch at the next falling (or rising)
edge of SCK1n, and the data is output from the SO1n pin.
µ
Remark n = 0: PD78F0531, 78F0532, 78F0533
µ
n = 0, 1: PD78F0534, 78F0535, 78F0536, 78F0537, 78F0537D
CHAPTER 16 SERIAL INTERFACES CSI10 AND CSI11
Figure 16-11. Output Operation of First Bit (1/2)
(a) Type 1: CKP1n = 0, DAP1n = 0
SCK1n
SOTB1n
SIO1n
SO1n
(b) Type 3: CKP1n = 1, DAP1n = 0
SCK1n
SOTB1n
SIO1n
SO1n
Preliminary User's Manual U17260EJ3V1UD
First bit 2nd bit
First bit 2nd bit
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