Pin Configuration - NEC mPD780208 Subseries User Manual

(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.
Clock output
(Clock input)
N-ch open-drain
SO0
SI0
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.
242
CHAPTER 13 SERIAL INTERFACE CHANNEL 0
Figure 13-25. Pin Configuration
Master device
SCK0
SB0 (SB1)
User's Manual U11302EJ4V0UM
SCK0
Serial clock
V
DD
R
L
N-ch open-drain
SB0 (SB1)
Serial data bus
Slave device
(Clock output)
Clock input
SO0
SI0