PLTW Digital Electronics : ALL Key Terms

DeMorgan's Theorems

1) Theorem stating that the complement of a sum (OR operation) equals the product (AND operation) of the complements, and 2) Theorem stating that the complement of a product (AND operation) equals the sum (OR operation) of the complements.

Sign Bit

A binary bit that is added to the leftmost position of a binary number to indicate whether that number represents a positive or a negative quantity.

Signed Binary Number

A binary number of fixed length whose sign is represented by one bit, usually the most significant bit, and whose magnitude is represented by the remaining bits.

Breadboard

A circuit board for wiring temporary circuits, usually used for prototypes or laboratory work.

Multiplexer

A circuit that directs one of several digital signals to a single output, depending on the states of several select inputs.

De-multiplexer

A circuit that uses a binary decoder to direct a digital signal from a single source to one of several destinations.

Design Specifications

A detailed description, especially one providing information needed to make, build, or produce something.

Logic Diagram

A diagram, similar to a schematic, showing the connection of logic gates.

Encoder

A digital circuit that produces an output code depending on which of its inputs is activated.

Complex PLD (CPLD)

A digital device consisting of several programmable sections with internal interconnections between the sections.

Transistor-Transistor (TTL)

A family of digital logic devices whose basic element is the bipolar junction transistor.

Engineering Notation

A floating point system in which numbers are expressed as products consisting of a number greater than one multiplied by an appropriate power of ten that is some multiple of three.

2's Complement

A form of signed binary notation in which negative numbers are created by adding 1 to the 1's complement form of the number.

1's Complement

A form of signed binary notation in which negative numbers are created by complementing all bits of a number, including the sign bit.

JTAG Port

A four-wire interface specified by the Joint Test Action Group (JTAG) used for loading test data or programming data into a PLD installed in a circuit.

Karnaugh Map

A graphical tool for finding the maximum SOP or POS simplification of a Boolean expression. A Karnaugh map works by arranging the terms of an expression so that variable scans are cancelled by grouping minterms or maxterms.

Truth Table

A list of all possible input values to a digital circuit, listed in ascending binary order, and the output response for each input combination.

Current

A movement of electrical charges around a closed path or circuit.

Octal Number System

A number system that has a base of 8; digits from 0 to 7 are used to express an octal number.

Digital Multi-Meter(DMM)

A piece of test equipment used to measure voltage, current, and resistance in an electronic circuit.

Oscilloscope

A piece of test equipment used to view and measure a variety of different waveforms.

Datasheet

A printed specification giving details of the pin configuration, electrical properties, and mechanical profile of an electronic device.

Minterm

A product term in a Boolean expression where all possible variables appear once in true or complement form.

Fuse

A protective device in the current path that melts or breaks when current exceeds a predetermined maximum value.

Cycle

A series of events that are regularly repeated in the same order.

Digital Waveform

A series of logic 1s and 0s plotted as a function of time.

Common Anode Display

A seven-segment LED display where the anodes of all the LEDs are connected to the circuit supply voltage. Each segment is illuminated by a logic LOW at its cathode.

Common Cathode Display

A seven-segment display in which the cathodes of all the LEDs are connected together and grounded. A logic HIGH illuminates a segment when applied to its anode.

Plastic Leaded Chip Carrier (PLCC)

A square IC package with leads on all four sides designed for surface mounting on a circuit board.

Maxterm

A sum term in a Boolean expression where all possible variables appear once in true or complement form.

Product Term

A term in a Boolean expression where one or more true or complement variables are AND'ed.

Sum Term

A term in a Boolean expression where one or more true or complement variables are OR'ed.

Sum-of-Products (SOP)

A type of Boolean expression where several product terms are summed (OR'ed) together.

Product-of-Sums (POS)

A type of Boolean expression where several sum terms are multiplied (AND'ed) together.

Digital

A way of representing a physical quantity by a series of binary numbers. A digital representation can have only specific discrete values.

Analog

A way of representing some physical quantity, such as temperature or velocity, by a proportional continuous voltage or current. An analog voltage or current can have any value within a defined range.

SI Notation

Abbreviation of System International, a system of practical units based on the meter, kilogram, second, ampere, Kelvin, mole, and candela.

Inverter

Also called a NOT gate or an inverting buffer. A logic gate that changes its input logic level to the opposite state.

NOT Gate

Also called an INVERTER gate or an inverting buffer. A logic gate that changes its input logic level to the opposite state.

Small Outline IC (SOIC)

An IC package similar to a DIP, but smaller, which is designed for automatic placement and soldering on the surface of a circuit board.

Large Scale Integration (LSI)

An IC that contains circuitry equivalent to 100 gates or more.

Medium Scale Integration (MSI)

An IC that contains circuitry equivalent to more than 11 and less than 100 gates.

Boolean Expression

An algebraic expression made up of Boolean variables and operators, such as AND (-), OR (+), or NOT (-). Also referred to as Boolean function or a logic function.

Square Wave

An almost instantaneous rise and decay of voltage or current in a periodic pattern with time and with a constant peak value.

Seven-Segment Display

An array of seven independently controlled light-emitting diodes (LED) or liquid crystal display (LCD) elements, shaped like a figure-8, which can be used to display decimal digits and other characters by turning on the appropriate elements.

Capacitor

An electrical device used to store electrical charge.

Integrated Circuit (IC)

An electronic circuit having many components, such as transistors, diodes, resistors, and capacitors, in a single package.

Logic Gate

An electronic circuit that performs a Boolean algebraic function.

Small-Scale Integration (SSI)

An integrated circuit having 12 or fewer gates in one package.

Logic Circuit

Any circuit that behaves according to a set of logic rules.

Fitting

Assigning internal PLD circuitry, and input and output pins, to a PLD design.

Hexadecimal Number System

Base-16 number system. Hexadecimal numbers are written with sixteen digits, 0-9 and A-F, with power-of-16 positional multipliers.

Field Programmable Gate Array (FPGA)

Class of PLDs that contain an array of more complex logic cells that can be very flexibly interconnected to implement high-level logic circuits.

Resistor Color Code

Coding system of colored stripes on a resistor to indicate the resistor's value and tolerance.

AND Gate

Digital circuit that implements the AND operation. The output of this circuit is HIGH only if all of its inputs are HIGH.

OR Gate

Digital circuit that implements the OR operation. The output of this circuit is HIGH (logic level 1) if any or all of its inputs are HIGH.

Combinational Logic

Digital circuitry in which an output is derived from the combination of inputs, independent of the order in which they are applied.

Distributive Property

Full name: distributive property of multiplication over addition. The property that allows us to distribute ("multiply through") an AND across several OR functions. For example, a(b+c)=ab+ac.

Ohm's Law

In electric circuits, I=V/R.

Printed Circuit Board

Insulating board containing conductive tracks for circuit connections.

JEDEC

Joint Electron Device Engineering Council.

LED

Light-emitting diode. An electronic device that conducts current in one direction only and illuminates when it is conducting.

NAND Gate

Logic circuit that operates like an AND gate followed by an INVERTER. The output of a NAND gate is LOW (logic level 0) only if all inputs are HIGH (logic level 1).

NOR Gate

Logic circuit that operates like an OR gate followed by an INVERTER. The output of a NOR gate is LOW (logic level 0) when any or all inputs are HIGH (logic level 1).

Full Adder

Logic circuit with three inputs and two outputs. The inputs are a carry bit (CIN) from a previous stage, a bit from the augend, and a bit from the addend, respectively. The outputs are the sum bit and the carry-out bit (COUT) produced by the addition of the bit from the addend with the bit from the augend and CIN.

Half Adder

Logic circuit with two inputs and two outputs. The inputs are a bit from the augend and a bit from the addend. The outputs are the sum bit produced by the addition of the bit from the addend with the bit from the augend and the resulting carry (COUT) bit, which will be added to the next stage.

Solder

Metallic alloy of tin and lead that is used to join two metal surfaces.

Scientific Notation

Numbers entered as a number from one to ten multiplied by a power of ten.

Sine Wave

One in which amplitude varies in proportion to the sine function of an angle.

Dual In-Line Package (DIP)

One style of integrated circuit package which has two rows of lead.

Series Circuit

One that has only one path current.

Parallel Circuit

One that has two or more branches for separate current from one voltage source.

Resistance

Opposition to current. Unit is the ohm.

Soldering

Process of joining two metallic surfaces to make an electrical contact by melting solder (usually tin and lead) across them.

Don't Care Condition

Situation when a circuit's output level for a given set of input conditions can be assigned as either a 1 or 0.

Schottky TTL

TTL subfamily that uses the basic TTL standard circuit except that it uses a Schottky barrier code (SBD) connected between the base and the collector of each transistor for faster switching.

555 Timer

TTL-compatible IC that can be wired to operate in several different modes, such as a one-shot and an astable multivibra

Transistor

Term derived from "transfer resistor." Semiconductor device that can be used as an amplifier or as an electronic switch.

Simulation

Testing design function by specifying a set of inputs and observing the resultant outputs. Simulation is generally shown as a series of input and output waveforms.

Kirchhoff's Current Law (KCL)

The algebraic sum of all currents into and out of any branch point in a circuit must equal zero.

Kirchhoff's Voltage Law (KVL)

The algebraic sum of all voltages around any closed path must equal zero.

Conventional Current

The direction of current flow associated with positive charge in motion. The current flow direction is from a positive to negative potential, which is in the opposite direction of electron flow.

Logic HIGH

The higher of two voltages in a digital system with two logic levels.

Amplitude

The instantaneous voltage of a waveform. Often used to mean maximum amplitude, or peak voltage, or a pulse.

Most Significant Bit (MSB)

The leftmost bit in a binary number. This bit has the number's largest positional multiplier.

Logic LOW

The lower of two voltages in a digital system with two logic levels.

Tinning

The process of applying a thin coat of solder to materials prior to their being soldered; for example, application of a light coat of solder to the filaments of a conductor to hold the filaments in place prior to soldering the conductor.

Design Entry

The process of using software tools to describe the design requirements of a PLD. Design entry can be done by entering a schematic or a text file that describes the required digital function.

Compiler

The process used by CPLD design software to interpret design information (such as a schematic or text file) and create required programming information for a CPLD.

Least Significant Bit (LSB)

The rightmost bit of a binary number. This bit has the number's smallest positional multiplier.

Cell

The smallest unit of Karnaugh map, corresponding to one line of a truth table. The input variables are the cell's coordinates and the output variable is the cell's contents.

SolderBridge

The unwanted formation of a conductive path of solder between conductors.

Toggle

To switch from one effect, feature, or state to another.

Soldering Iron

Tool with an internal heating element used to heat surfaces being soldered to the point where the solder becomes molten.

Adjacent Cell

Two cells in a K-map are adjacent if there is only one variable that is different between the coordinates of the two cells.

Exclusive-OR (XOR) Circuit

Two-input logic circuit that produces a high output only when the inputs are different.

Exclusive-NOR (XNOR) Circuit

Two-input logic circuit that produces a high output only when the inputs are equal.

Hertz (Hz)

Unit of frequency. One hertz equals one cycle per second.

Ohm

Unit of resistance. Value of one ohm allow current of one ampere with potential difference of one volt.