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In addition to the converters, many embedded microprocessors in-
clude a variety of timers as well. One of the most common types of
timers is the Programmable Interval Timer (PIT). A PIT just counts
down from some value to zero. Once it reaches zero, it sends an in-
terrupt to the processor indicating that it has finished counting. This
is useful for devices such as thermostats, which periodically test the
temperature around them to see if they need to turn the air condi-
tioner on, the heater on, etc.
Universal Asynchronous Receiver/Transmitter (UART) block makes
it possible to receive and transmit data over a serial line with very
little load on the CPU. Dedicated on-chip hardware also often inclu-
des capabilities to communicate with other devices (chips) in digital
formats such as I2C and Serial Peripheral Interface (SPI).
The Arduino system provides us with 14 digital I/O-lines, 7 analog
I/O-lines.