 2000 Microchip Technology Inc.

DS39504A-page 4-9

Section 4 Architecture

4

INT0

I

ST

External Interrupt0

INT1

I

ST

External Interrupt1

INT2

I

ST

External Interrupt2

LB

O

—

System bus low byte strobe

LVDIN

I

Analog

Low voltage detect input

MCLR

I/P

ST

Master clear (reset) input or programming voltage input. This pin is

an active low reset to the device.

NC

—

—

These pins should be left unconnected.

OE

O

—

System bus output enable strobe

OSC1

I

ST/CMOS

Oscillator crystal input or external clock source input. ST buffer when

configured in RC mode. CMOS otherwise.

OSC2

O

—

Oscillator crystal output. Connects to crystal or resonator in crystal

oscillator mode. In RC mode, OSC2 pin outputs CLKOUT, which has

1/4 the frequency of OSC1, and denotes the instruction cycle rate.

PSP0

I/O

TTL

Parallel Slave Port for interfacing to a microprocessor port. These

pins have TTL input buffers when PSP module is enabled.

PSP1

I/O

TTL

PSP2

I/O

TTL

PSP3

I/O

TTL

PSP4

I/O

TTL

PSP5

I/O

TTL

PSP6

I/O

TTL

PSP7

I/O

TTL

PORTA is a bi-directional I/O port.

RA0

I/O

TTL

RA1

I/O

TTL

RA2

I/O

TTL

RA3

I/O

TTL

RA4

I/O

ST

RA4 is an open drain when configured as output.

RA5

I/O

TTL

RA6

I/O

TTL

PORTB is a bi-directional I/O port. PORTB can be software pro-

grammed for internal weak pull-ups on all inputs.

RB0

I/O

TTL

RB1

I/O

TTL

RB2

I/O

TTL

RB3

I/O

TTL

RB4

I/O

TTL

Interrupt on change pin.

RB5

I/O

TTL

Interrupt on change pin.

RB6

I/O

TTL/ST

Interrupt on change pin. Serial programming clock. TTL input

buffer as general purpose I/O, Schmitt Trigger input buffer when

used as the serial programming clock.

RB7

I/O

TTL/ST

Interrupt on change pin. Serial programming data. TTL input

buffer as general purpose I/O, Schmitt Trigger input buffer when

used as the serial programming data.

Table 4-1:

I/O Descriptions (Continued)

Pin Name

Pin

Type

Buffer

Type

Description

Legend: TTL = TTL-compatible input

CMOS = CMOS compatible input or output

ST = Schmitt Trigger input with CMOS levels

O = output

PU = Weak internal pull-up

I = input

Analog = Analog input or output

P = Power