P40 To P47 (Port 4); Reset; X1, X2; Regc - NEC switch User Manual

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
pin via 22 µ F 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 , V
DD0 DD1
These pins are positive power supply pins.
2.2.11 V , V
SS0 SS1
These pins are ground pins.
CHAPTER 2 PIN FUNCTIONS
User's Manual U12978EJ3V0UD
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