
PIC18F2423/2523/4423/4523
DS39755C-page 18
2009 Microchip Technology Inc.
TABLE 1-3:
PIC18F4423/4523 PINOUT I/O DESCRIPTIONS
Pin Name
Pin Number
Pin
Type
Buffer
Type
Description
PDIP
QFN TQFP
MCLR/VPP/RE3
MCLR
VPP
RE3
118
18
I
P
I
ST
Master Clear (input) or programming voltage (input).
Master Clear (Reset) input. This pin is an active-low
Reset to the device.
Programming voltage input.
Digital input.
OSC1/CLKI/RA7
OSC1
CLKI
RA7
13
32
30
I
I/O
ST
CMOS
TTL
Oscillator crystal or external clock input.
Oscillator crystal input or external clock source input.
ST buffer when configured in RC mode;
analog otherwise.
External clock source input. Always associated with
pin function, OSC1. (See related OSC1/CLKI,
OSC2/CLKO pins.)
General purpose I/O pin.
OSC2/CLKO/RA6
OSC2
CLKO
RA6
14
33
31
O
I/O
—
TTL
Oscillator crystal or clock output.
Oscillator crystal output. Connects to crystal
or resonator in Crystal Oscillator mode.
In RC mode, OSC2 pin outputs CLKO, which
has 1/4 the frequency of OSC1 and denotes
the instruction cycle rate.
General purpose I/O pin.
Legend: TTL = TTL compatible input
CMOS = CMOS compatible input or output
ST
= Schmitt Trigger input with CMOS levels
I
= Input
O
= Output
P
= Power
I2C= I2C/SMBus
Note 1: Default assignment for CCP2 when Configuration bit, CCP2MX, is set.
2: Alternate assignment for CCP2 when Configuration bit, CCP2MX, is cleared.