Samsung KS57C2308 Manual page 216

I/O PORTS
PORT 0 CIRCUIT DIAGRAM
PUMOD.0
P0.0/INT4
SCK
P0.1/
P0.2/SO
P0.3/SI
NOTE:
10-6
V
DD
SCK
When and SO act as an output, its pull-up resistor is automatically
disabled, even though the port's pull-up resistor is enabled by bit settings
to the pull-up resistor mode register (PUMOD).
Figure 10-1. Port 0 Circuit Diagram
SCK
SO
KS57C2308/P2308/C2316/P2316
SCK
INT4 SI
SMOD
8