TRUTH TABLES AND EXERCISES
Figure 12 Logic Gate Status Notation
Reading Logic Diagrams
When reading logic prints the reader usually must decide the input values to each gate. But
occasionally the print will provide information as to the normal state of each logic gate. This
is denoted by a symbol similar to the bistable symbol, as shown in Figure 12. The symbol is
drawn so that the first part of the square wave indicates the normal state of the gate. The
second part of the square wave indicates the off-normal state of the gate. Figure 12 also
illustrates how this notation is applied.
Reading a logic diagram that does not provide information on the status of the gates is not any
more difficult. It simply requires the reader to choose the initial conditions, determine the
response of the circuits, and modify the inputs as needed. The following exercises will illustrate
how to read some simple logic diagrams.
To aid in understanding the material presented in this module, practice reading the following
logic diagrams by answering the questions. The answers are on page 18.