Digital electronics is one of the fundamental courses found in all electrical engineering and most science programs. The great variety of LabVIEW Boolean and numeric controls/indicators, together with the wealth of programming structures and functions, make LabVIEW an excellent tool to visualize and demonstrate many of the fundamental concepts of digital electronics. The inherent modularity of LabVIEW is exploited in the same way that complex digital integrated circuits are built from circuits of less complexity, which in turn are built from fundamental gates. This manual is designed as a teaching resource to be used in the classroom as demonstrations, in tutorial sessions as collaborative studies, or in the laboratory as interactive exercises. The order of the labs follows most electronic textbooks. The first six labs cover the fundamental circuits of gates, encoders, binary addition, D-latches, ring counters, and JK flip-flops. Many of the VIs are suitable for both classroom demonstration and laboratory exploration. The second set of six labs cover advanced topics such as DACs, ADCs, seven-segment displays, serial communication, and the CPU. These are best done in the context of a digital electronics lab, comparing the LabVIEW
simulations with real integrated circuits. In each case, you can enhance simulations presented in the text by using a National Instruments DAQ board to interact with the real world through LabVIEW digital I/O, analog out, analog in, and serial VIs. Labs 2, 5, and 12 are application oriented and are designed to demonstrate encoding schemes, digital encryption, and the operation of a CPU. These labs could be presented as challenging problems in a tutorial setting or in a
workshop environment. The labs can also be grouped to demonstrate special relationships of
advanced devices on certain basic gates. For example, the CPU operation is dependent on the concept of registers and two input operations. This manual includes a complete set of LabVIEW VIs. The text is also included on the CD so that you can customize the material. Gates are the fundamental building blocks of digital logic circuitry. These devices function by “opening” or “closing” to admit or reject the passage of a logical signal. From only a handful of basic gate types (AND, OR, XOR, and NOT), a vast array of gating functions can be created.
The AND Gate
A basic AND gate consists of two inputs and an output. If the two inputs are A and B, the output (often called Q) is “on” only if both A and B are also “on.” In digital electronics, the on state is often represented by a 1 and the off state by a 0. The relationship between the input signals and the output signals is often summarized in a truth table, which is a tabulation of all possible inputs
and the resulting outputs. For the AND gate, there are four possible combinations of input states: A=0, B=0; A=0, B=1; A=1, B=0; and A=1, B=1. In the following truth table, these are listed in the left and middle columns. The AND gate output is listed in the right column.
In LabVIEW, you can specify a digital logic input by toggling a Boolean switch; a Boolean LED indicator can indicate an output. Because the AND gate is provided as a basic built-in LabVIEW function, you can easily wire two switches to the gate inputs and an indicator LED to the output to produce a simple VI that demonstrates the AND gate.
