PICDEM2 datasheet(51/60 Pages) MICROCHIP

51 / 60 page

PICDEM 2 User’s Guide

DS30374D-page 46

 2001 Microchip Technology Inc.

A.4

RS-232 Serial Port

An RS-232 level shifting IC has been provided with all necessary hardware to

support connection of an RS-232 host through the DB9 connector. The port is

configured as DCE, and can be connected to a PC using a straight through

cable.

The PIC16C74 has its RX and TX pins tied to the RX and TX lines of the

MAX232A.

A.5

Switches

Three switches provide the following functions:

• S1 - MCLR to hard reset the processor

• S2 - Active low switch connected to RA4

• S3 - CCP1 for capture of timer

Switches S1 and S3 have debounce capacitors whereas S2 does not,

allowing the user to investigate debounce techniques.

When pressed, the switches are grounded. When idle, they are pulled high

(+5V).

A.6

Oscillator Options

• RC oscillator (2MHz approximately) supplied. This oscillator may be

disabled by removing jumper J7.

• Pads provided for user furnished crystal and two capacitors.

• Socket provided for clock oscillator.

Provisions are also provided for an external crystal oscillator for Timer1.

A.7

Analog Input

A 5K ohm potentiometer is connected through a series 470 ohm resistor to

AN0.

The pot can be adjusted from VDD to GND to provide an analog input to the

parts with an A/D module.

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