NEC switch - Manual (Page 31)

CHAPTER 2 PIN FUNCTIONS
User’s Manual U12978EJ3V0UD
31
2.2.4 P40 to P47 (Port 4)
These pins constitute an 8-bit I/O port. In addition, they also function as key return signal detection pins.
The following operation modes can be specified in 1-bit units.
(1) Port mode
In this mode, port 4 functions as an 8-bit I/O port. Port 4 can be set to the input or output mode in 1-bit units by
using port mode register 4 (PM4). When used as an input port an on-chip pull-up resistor can be used by
setting pull-up resistor option register 0 (PU0).
(2) Control mode
In this mode, the pins function as key return signal detection pins (KR00 to KR07).
2.2.5 RESET
This pin inputs an active-low system reset signal.
2.2.6 X1, X2
These pins are used to connect a crystal resonator for system clock oscillation.
To supply an external clock, input the clock to X1 and input the inverted signal to X2.
2.2.7 REGC
This pin is a power supply pin for driving a USB driver/receiver generated internally. Connect this pin to the V
SS
pin via 22 µF capacitor.
2.2.8 USBDM
This pin (negative side) inputs or outputs serial data for the USB function.
2.2.9 USBDP
This pin (positive side) inputs or outputs serial data for the USB function.
2.2.10 V
DD0
, V
DD1
These pins are positive power supply pins.
2.2.11 V SS0 , V SS1
These pins are ground pins.