Skip to Content
Introduction to Digital Systems: Modeling, Synthesis, and Simulation Using VHDL
book

Introduction to Digital Systems: Modeling, Synthesis, and Simulation Using VHDL

by Mohammed Ferdjallah
July 2011
Intermediate to advanced content levelIntermediate to advanced
225 pages
6h 22m
English
Wiley
Content preview from Introduction to Digital Systems: Modeling, Synthesis, and Simulation Using VHDL

3.6 LOGIC REPRESENTATIONS AND CIRCUIT DESIGN

Logic gates are used to represent and implement logic expression into digital circuit diagrams. Consider the following logic function:

images

The digital circuit (Figure 3.4) implements the function f. The digital circuit consists of elementary logic functions, which are implicit in the logic function. The conversion from logic expressions to circuit diagrams obeys the operator precedence rules shown in Figure 3.5. These precedence rules dictate the order in which the implicit elementary logic functions are implemented.

Notice that logic expressions within parentheses are converted first. The implementation of the elementary logic functions within the parentheses obeys the precedence rules as well. In all cases, the NOT function is implemented first, then the AND function, then the OR function. Similarly, a digital circuit can be converted to a logic expression. The logic function of the digital circuit is found by propagating the input variables through the gates to the output of the circuit. The logic output expression of a gate is determined by the logic expressions at its inputs. Consider the digital circuit shown in Figure 3.6. The logic expression, which represents the logic circuit diagram in Figure 3.6, is expressed as

images

Figure 3.1 NOT, ...

Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
and much more.
Start your free trial

You might also like

Digital Systems Design with FPGAs and CPLDs

Digital Systems Design with FPGAs and CPLDs

Ian Grout
Synthesis of Arithmetic Circuits: FPGA, ASIC and Embedded Systems

Synthesis of Arithmetic Circuits: FPGA, ASIC and Embedded Systems

Jean-Pierre Deschamps, Gery J.A. Bioul, Gustavo D. Sutter

Publisher Resources

ISBN: 9780470900550Purchase book