NEC mPD780344 Series, Руководство пользователя

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User’s Manual U15798EJ2V0UD
CHAPTER 15 SERIAL INTERFACE CSI1
(4) Timing of output to SO1 pin (first bit)
When communication is started, the value of transmit buffer register 1 (SOTB1) is output from the SO1 pin. The
output operation of the first bit at this time is explained below.
Figure 15-6. Output Operation of First Bit
(1) CKP1 = 0, DAP1 = 0 (or CKP1 = 1, DAP1 = 0)
SCK1
SOTB1
SIO1
Output latch
SO1
Writing to SOTB1 or
reading from SIO1
First bit Second bit
The first bit is directly latched to the output latch from the SOTB1 register at the falling (or rising) edge of SCK1,
and is output from the SO1 pin via the output selector. At the next rising (or falling) edge of SCK1, the value
of the SOTB1 register is transferred to the SIO1 register and shifted by 1 bit. At the same time, the first bit of
the receive data is stored in the SIO1 register via the SI1 pin.
The second and subsequent bits are latched to the output latch from SIO1 at the next falling (or rising) edge of
SCK1 and the data is output from the SO1 pin.
(2) CKP1 = 0, DAP1 = 1 (or CKP1 = 1, DAP1 = 1)
First bit Second bit Third bit
SCK1
SOTB1
SIO1
Output latch
SO1
Writing to SOTB1 or
reading from SIO1
The first bit is directly output from the SOTB1 register to the SO1 pin via the output selector at the falling edge
of the write signal of SOTB1 or the read signal of the SIO1 register. At the next falling (or rising) edge of SCK1,
the value of the SOTB1 register is transferred to the SIO1 register and shifted by 1 bit. At the same time, the
first bit of the received data is stored in the SIO1 register via the SI1 pin.
The second and subsequent bits are latched to the output latch from SIO1 at the next rising (or falling) edge of
SCK1 and the data is output from the SO1 pin.