AN887 Datasheet, PDF (3/12 Pages) STMicroelectronics – MICROCONTROLLERS MADE EASY

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
SYNCHRONOUS
ASYNCHRONOUS
CLOCK
b b b b b b b ^DATA
0b
Start
bb
bb 1
Stop
CLOCK
+
DATA
VR02101C
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
Voltage
5
4
3
2
1
ANALOG
ANALOG
SIGNAL
A/D
CONVERTER
DIGITAL
5 42 112
Time
VR02101D
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