Parallax SX20AC/SX28AC

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© Parallax Inc.

Page 6 of 51

Rev 1.6 11/20/2006

2.0

CONNECTION DIAGRAMS

2.1.

Pin Assignments

Figure 2-1: Pin Assignments

2.2.

Pin Descriptions

Table 2-1: Pin Descriptions

Name

Pin Type

Input Levels

Description

RA0

I/O

TTL/CMOS

Bidirectional I/O Pin; symmetrical source / sink capability

RA1

I/O

TTL/CMOS

Bidirectional I/O Pin; symmetrical source / sink capability

RA2

I/O

TTL/CMOS

Bidirectional I/O Pin; symmetrical source / sink capability

RA3

I/O

TTL/CMOS

Bidirectional I/O Pin; symmetrical source / sink capability

RB0

I/O

TTL/CMOS/ST

Bidirectional I/O Pin; comparator output; MIWU/Interrupt input

RB1

I/O

TTL/CMOS/ST

Bidirectional I/O Pin; comparator negative input; MIWU/Interrupt input

RB2

I/O

TTL/CMOS/ST

Bidirectional I/O Pin; comparator positive input; MIWU/Interrupt input

RB3

I/O

TTL/CMOS/ST

Bidirectional I/O Pin; MIWU/Interrupt input

RB4

I/O

TTL/CMOS/ST

Bidirectional I/O Pin; MIWU/Interrupt input

RB5

I/O

TTL/CMOS/ST

Bidirectional I/O Pin; MIWU/Interrupt input

RB6

I/O

TTL/CMOS/ST

Bidirectional I/O Pin; MIWU/Interrupt input

RB7

I/O

TTL/CMOS/ST

Bidirectional I/O Pin; MIWU/Interrupt input

RC0

I/O

TTL/CMOS/ST

Bidirectional I/O Pin

RC1

I/O

TTL/CMOS/ST

Bidirectional I/O Pin

RC2

I/O

TTL/CMOS/ST

Bidirectional I/O Pin

RC3

I/O

TTL/CMOS/ST

Bidirectional I/O Pin

RC4

I/O

TTL/CMOS/ST

Bidirectional I/O Pin

RC5

I/O

TTL/CMOS/ST

Bidirectional I/O Pin

RC6

I/O

TTL/CMOS/ST

Bidirectional I/O Pin

RC7

I/O

TTL/CMOS/ST

Bidirectional I/O Pin

RTCC

I

ST

Input to Real-time Clock/counter

MCLR

I

ST

Master Clear reset input – active low. When not controlled externally, this pin must

be pulled high with a 10 kΩ resistor.

OSC1/In/Vpp

I

ST

Crystal oscillator input; external clock source input

OSC2/Out

O

CMOS

Crystal oscillator output; in R/C mode, internally pulled to Vdd through weak pull-up

Vdd

P

-

Positive supply pin

Vss

P

-

Ground pin

Note: I = input, O = output, I/O = Input/Output, P = Power, TTL = TTL input, CMOS = CMOS input, ST = Schmitt Trigger input, MIWU =

Multi-Input Wakeup input.