Mechanical Switches

Mechanical switches are useful for direct input to digital circuits. One of the more convenient versions is a bank of rocker switches pac...

Multiplexed Bus

In order to describe the timing of such a shared data bus, it is necessary to define some notation for timing diagrams. The notation used...

Tri-State Logic

Tri-state logic does not refer to orderly thinking in a three state geographic region! When we speak of binary (base two number) values, ...

CMOS logic

CMOS logic ( complementary symmetry MOS ) is another form of MOS logic. It has advantages over NMOS logic for low power circuitry and for...

NMOS Logic

The conductive state of the FET's channel is what allows or prevents current from flowing in the device. For a typical logic N-channe...

The FET as a Logic Switch

Most of the logic devices used in highly integrated circuits do not use bipolar transistors. Instead, they use field effect transistors....

Transistor Switch OFF

When the input is connected to logic zero (ground voltage), no current flows into the base of the transistor, since its base and emitter t...

Transistor Switch ON

Transistors can be configured to function as switches. As can be seen in figure bellow, an NPN transistor operating as a current controlled ...

Digital Hardware Concepts

In addition to the CPU, memory, and I/O building blocks, other logic circuits may also be required. Such logic circuits are frequently re...

The Design and Development Process

Structured design of a microcomputer requires the ability to do the system design and partitioning from the top down while implementing th...

Logic Symbols

Logic symbols are used to represent the logic functions in a more abstract way, allowing the designer to specify the logical function of a...

Microcomputer and Microcontroller Architectures

Microprocessors are generally utilized for relatively high performance applications where cost and size are not critical selection criter...

Diode

The diode is a simple semiconductor device acting as a "one way" current valve. It only lets current flow in one direction. F...

Transistors

The flow analogy can also be used to model how a transistor operates in a logic circuit. The transistor is an amplifier. It uses a small a...

Voltage, Current, and Resistance

Fig 1. Voltage in an electrical circuit is analogous to pressure in a fluid. In figure 1, a battery provides a voltage source for e...

Timing Diagrams

The timing diagram is the standard "language" of illustrating timing relationships between different parts of a design. In ord...