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MICROCONTROLLERS MADE EASY

SERIAL INTERFACE

Serial interface are used to exchange data with the external world. Many microcontrollers

have both asynchronous and synchronous communications peripherals built in. Usually, an

asynchronous interface is called a serial communication interface (SCI or UART) while the

synchronous interface is called a serial peripheral interface (SPI). A typical SCI application is

to connect a PC for debugging purpose while a typical SPI application is to connect an ex-

ternal EEPROM.

A synchronous bus includes a separate line for the clock signal which simplifies the transmitter

and receiver but is more susceptible to noise when used over long distances. With an asyn-

chronous bus the transmitter and receiver clocks are independent, and a resynchronization is

performed for each byte at the start bit.

Figure 3. Synchronous and Asynchronous Communication Principles

A/D CONVERTER

Converts an external analog signal (typically relative to voltage) into a digital representation.

Microcontrollers that have this feature can be used for instrumentation, environmental data

logging, or any application that lives in an analog world.

Figure 4. A/D Converter Principle

VR02101C

SYNCHRONOUS

ASYNCHRONOUS

0b

b

b

b

b1

CLOCK

bb

b

DATA

CLOCK

+

DATA

b

b

Start

Stop

bb

VR02101D

ANALOG

1

2

3

4

5

ANALOG

SIGNAL

Time

54

2

11

2

DIGITAL

Voltage

A / D

CONVERTER