NEC mPD780208 Subseries, Руководство пользователя

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CHAPTER 13 SERIAL INTERFACE CHANNEL 0
242
User’s Manual U11302EJ4V0UM
(5) Pin configuration
The serial clock pin SCK0 and serial data bus pin SB0 (SB1) have the following configurations.
(a) SCK0: Serial clock I/O pin
[1] Master: CMOS and push-pull output
[2] Slave: Schmitt input
(b) SB0 (SB1): Serial data I/O alternate-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 13-25. Pin Configuration
Caution Because the N-ch open-drain output must be high impedance at the time of data
reception, write FFH to serial I/O shift register 0 (SIO0) in advance. The N-ch open-
drain output can be high impedance throughout transfer. However, when the wakeup
function specification bit (WUP) = 1, the N-ch open-drain output is always high
impedance. Thus, it is not necessary to write FFH to SIO0.
SI0
SO0
SI0
SO0
(Clock input)
Clock output
Master device
Clock input
(Clock output)
Serial clock
SCK0 SCK0
R
L
Serial data bus
SB0 (SB1) SB0 (SB1)
N-ch open-drain N-ch open-drain
Slave device
V
DD