User's Manua switch

CHAPTER 2 PIN FUNCTIONS
User’s Manual U12978EJ3V0UD
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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 VSS
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
DD0, VDD1
These pins are positive power supply pins.
2.2.11 V
SS0, VSS1
These pins are ground pins.