Page 222 - Mechatronics with Experiments

208 MECHATRONICS
Embedded engine controller Monitor

Engine

Computer
Printer

Mouse
Keyboard
(a)

An embedded controller,
typically called “electronic
control module” (ECM)

I/O Connector
(b)
FIGURE 4.1: (a) Comparison of an embedded computer and a non-embedded computer. The
embedded computer has just enough resources for the application, must operate in a harsh
environment, has a smaller physical size and has hard real-time requirements. (b) Picture of a
rugged “embedded controller” used in off-highway equipment applications.

a hard disk drive, floppy disk drive, CD/DVD drive, and tape drive for permanent
data storage, whereas an embedded computer may have battery backed RAM or flash
or ROM memory to store just the application software. Embedded microcontrollers
have limited resources in terms of power (i.e., they may be powered by a battery),
memory, and CPU speed. Embedded computers are dedicated to specific tasks. They
do not store general purpose programs such as word processors, graphics programs,
and so on.
3. Embedded controllers and I/O interfaces are more integrated at the chip design
level than general purpose computers, that is I/O interface channels such as analog to
digital (ADC) and digital to analog (DAC) converters are integrated into the microchip
hardware.
4. The physical size of the embedded computer is typically required to be very small,
which may be dictated by the application.
5. Embedded controllers operate in extreme environmental conditions (i.e., an embedded
controller for a diesel engine must operate under conditions of large temperature and
vibration variations).
6. Embedded computers invariably incorporate a watchdog timer circuit to reset the
system in case of a failure.
7. Embedded microcontrollers may have a dedicated debugging circuit on the chip so
that the timing of all the I/O signals can be checked and the application program