NEC 78014Y Series, User Manual

Page: 363 / 547

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CHAPTER 16 SERIAL INTERFACE CHANNEL 0 (
µ
PD78014Y Subseries)
363
(5) Pin configuration
The serial clock pin SCK0 and serial data bus pin SB0 (SB1) have the following configurations.
(a) SCK0 : Serial clock input/output pin
<1> Master : CMOS and push-pull output
<2> Slave : Schmitt input
(b) SB0 (SB1) : Serial data input/output dual-function pin
Both master and slave devices have an N-ch open-drain output and a Schmitt input.
Because the serial data bus line has an N-ch open-drain output, an external pull-up resistor is necessary.
Figure 16-28. Pin Configuration
Caution Because the N-ch open-drain output must be set to high-impedance at the time of data
reception, write FFH to the serial I/O shift register 0 (SIO0) in advance. However, when the wake-
up function specification bit (WUP) = 1, the N-ch open-drain output will always be set to high-
impedance. Thus, it is not necessary to write FFH to SIO0 before reception.
Master Device
Clock Output
(Clock Input)
N-ch Open-Drain
SO0
SI0
SCK0 SCK0
Serial Clock
SB0 (SB1)
R
L
SB0 (SB1)
Serial Data Bus
Slave Device
(Clock Output)
Clock Input
N-ch Open-Drain
SO0
SI0
V
DD