Page 57 - The Mechatronics Handbook

FIGURE 4.1 Voltage levels and logical values correspondence.

FIGURE 4.2 A finite state automaton: X—input binary vector, Y—output binary vector, Q—internal state vector.

4.2 Digital Logic

Digital circuits are composed of logic gates, such as elementary electronic circuits operating in only two
states. These gates operate in such a way that the resulting logical value corresponds to the resulting value
of the Boolean algebra statements. This means that with the help of gates we can realize every logical
and arithmetical operation. These operations are performed in combinational circuits for which the
resulting value is dependent only on the actual state of the inputs variables. Of course, logic gates are
not enough for automata construction. For creating an automaton, we also need some memory elements
in which we capture the responses of the arithmetical and logical blocks.
A typical scheme of a digital finite state automaton is given in Fig. 4.2. The automata can be constructed
from standard ICs containing logic gates, more complex combinational logic blocks and registers,
counters, memories, and other standard sequential ICs assembled on a printed circuit board. Another
possibility is to use application specific integrated circuits (ASIC), either programmable or full custom,
for a more advanced design. This approach is suitable for designs where fast hardware solutions are
preferred. Another possibility is to use microcontrollers that are designed to serve as universal automata,
which function can be specified by memory programming.

4.3 Overview of Control Computers
Huge, complex, and power-consuming single-room mainframe computers and, later, single-case mini-

computers were primarily used for scientific and technical computing (e.g., in FORTRAN, ALGOL) and
for database applications (e.g., in COBOL). The invention in 1971 of a universal central processing unit
(CPU) in a single chip microprocessor caused a revolution in the computer technology. Beginning in

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