Review of electrical circuits....
 

High level description of electrical circuits:

  • Has a number of (electrial) input signals
  • Has a number of (electrial) output signals
  • The output signals can change according to the function of the electrical circuit

Digital electrical circuits
 

High level description of digital electrical circuits:

  • Has a number of (electrial) discrete input signals
  • Has a number of (electrial) discrete output signals
  • The output signals can change according to the function of the electrical circuit

Signal values used in digital circuits
 

  • Digital circuit has 2 signal values for both inputs and outputs:

      • A low level signal (0 V) that represent the "false" logical value

        The low signal value is denoted by 0

      • A high level signal (5 V) that represent the "true" logical value

        The high signal value is denoted by 1

Number of possible input values to digital circuits

  • A digital circuit with N input signals has

      • 2N possible input (combination) values         

    E.g.: the input values for a digital circuit with 2 input signals: 

         00   01   10   11

Categories of digital circuits

The digital circuits are divided into 2 broad categories:

  1. Combinatorial digital circuits:

      • The output signals depend only on the current values of the input signals

        (The circuit does not have memory)

  2. Sequential digital circuits:

      • The output signals depend on (1) the current values of the input signals and (2) the state of the (digital) circuit

        (This kind of circuits have memory !!)

        (The state of the circuit is its memory....)

Summary

  • Categories of electrical circuits:

We will first study the combinatorial circuits...