Increasing levels of development and complexity: • Transistors built from semiconductors • Logic gates built from transistors • Logic functions built from gates • Flip-flops built from logic • Counters and sequencers from flip-flops • Microprocessors from sequencers • Computers from microprocessors
An electronic counter is characterised by its durable, easy to use, and compact design. • Adigital counter is an electronic counter that features a digital readout but is otherwise similar to a non-digital electronic counter. • A mechanical counter displays its results on mechanical wheels in contrast to a digital counter that uses a solid-state LCD or LED display. • Both LCD (Liquid Crystal Display) and LED (Light Emitting Diode)use the same basic display technology. The difference between the two is only how the display is illuminated. • LCD displays are not self-illuminating. They need a backlight in order to produce a visible picture. • LED Displays are technological advancement of LCD displays - they are the LCD displays with an LED backlight to power up the LCD panel. • It means that LEDs are placed behind or around the LCD panel to enhance the luminosity and video definition of the monitor screen.
A sequencer - an electronic device or software programme that can be instructed to order and modify digitally stored musical sounds for playback, as through a synthesizer. • "Flip-flop" is the common name given to two-state devices which offer basic memory for sequential logic operations. • Flip-flops are used for digital data storage and transfer, and are commonly used in banks called "registers" for the storage of binary numerical data.
Digital Logic is the basis of electronic systems, such as computers and cell phones. • Digital Logic is rooted in binary code, a series of zeroes and ones each having an opposite value. • This system facilitates the design of electronic circuits that convey information, including logic gates. • Digital Logic gate functions include and, or and not. The value system translates input signals into specific output. • Digital Logic facilitates computing, robotics and other electronic applications.
Digital Logic Design is basic to the fields of electrical engineering and computer engineering. • Digital Logic designers build complex electronic components that use both electrical and computational characteristics, e.g. power, current, logical function, protocol and user input. • Digital Logic Design is used to develop hardware, such as circuit boards and microchip processors. • This hardware processes user input, system protocol and other data in computers, navigational systems, cell phones or other high-tech systems.
Digital systems record 1 and 0 in several ways: • (a) CDs and DVDs represent 1 by the presence and 0 by the absence of a pit (or depression) in a layer of aluminium on a rigid plastic disk and detected by reflection of a laser beam. The same principle—presence or absence of a hole detected by a light sensor—was used in computer punch cards and paper tapes in early computers (and even before that). • (b) Magnetic Disks (and Data Storage Tapes) represent logic data with magnetised areas on an iron oxide recording surface. A south pole stickingout of the surface would represent a 1 and a north pole would be a 0 (orvice versa). • (c) Spring loaded mechanical switches have two states, closed and open. Either of these states could be chosen to represent truth; for example, thedesigner might interpret an open switch as a logic 1.
The electronically controlled switch – a fundamental digital device G = H x y G = L y x S S
Logic variables There are several ways of representinglogic functions: • Symbols to represent the gates • Truth tables • Boolean algebra