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Assurance Process for Complex Electronics

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Glossary

Antifuse

A two-terminal device that is normally a high resistive element and is programmed to a low impedance. 

Architecture

The common logic structure of a family of programmable integrated circuits. The same architecture may be realized in different manufacturing processes.

ASIC (Application Specific Integrated Circuit):

IC product customized for a single application.

Asynchronous

A signal whose data is acknowledged or acted upon immediately, irrespective of any clock signal.

Boundary scan

Boundary scan is a methodology allowing complete controllability and observability of the boundary pins of a JTAG-compatible device via software control. This capability enables in-circuit testing without the need of in-circuit test equipment.

Cell Library

The collective name for the set of logic functions defined by the manufacturer of an Application-Specific Integrated Circuit (ASIC). The designer decides which types of cells should be realized and connected together to make the device perform its desired function.

Chip

Another name for an integrated circuit.

Codec

Short for compressor/decompressor, a codec is any technology for compressing and decompressing data. Codecs can be implemented in software, hardware, or a combination of both. Some popular codecs for computer video include MPEG, Indeo and Cinepak. 

Combinatorial

A digital function whose output value is directly related to the current combination of values on its inputs. Also known as combinational.

Comparator (digital)

A logic function that compares two binary values, and outputs the results in terms of binary signals representing less-than and/or equal-to and/or greater-than.

Configurable/Complex Logic Block (CLB)

The array of multi-input and multi-output logic cells to be programmed. CLB is a configurable logic block that consists mainly of Look-up Tables (LUTs) and flip flops. 

Cores

In the semiconductor design industry, refers to predefined functions such as processors or bus interfaces that are typically licensed from the software developer. Cores can be implemented directly in silicon, either in fixed logic or programmable logic devices, and saves chip designers time during product development. Synonymous with Intellectual Property.

CPLD (Complex Programmable Logic Device)

Programmable logic devices characterized by an architecture offering high speed, predictable timing and simple software.

Die

An unpackaged integrated circuit. In this case, the plural of die is also die.

Digital Signal

A digital signal is one whose key characteristic (e.g., voltage or current) fall into discrete ranges of values.  Most digital systems utilize two voltage levels (low and high values).

Digital Signal Processor (DSP)

A specialized CPU used for digital signal processing of signals such as sound, video, and other analog signals which have been converted to digital form. Some uses of DSP are to decode modulated signals from modems, to process sound, video, and images in various ways, and to understand data from sonar, radar, and seismological readings.

EEPROM (Electrically-Erasable Programmable Read-Only Memory)

A memory device whose contents can be electrically programmed by the designer. Additionally, the contents can be electrically erased allowing the device to be reprogrammed.

Electro-Static Discharge (ESD)

The term electro-static discharge refers to a charged person, or object, discharging static electricity. Although the current associated with such a static charge is low, the electric potential can be in the millions of volts and can severely damage electronic components.

EPROM (Erasable Programmable Read-Only Memory)

A memory device whose contents can be electrically programmed by the designer. Additionally, the contents can be erased by exposing the die to ultraviolet light through a quartz window mounted in the top of the component's package.

Falling-Edge

A transition from a logic 1 to a logic 0. Also known as a negative edge.

Firmware

Software programs, or sequences of instructions, that are hard-coded into non-volatile memory devices.

FIFO

First-in first-out

A data structure or hardware buffer where items come out in the same order they came in.

Flash memory

Non-volatile storage device similar to EEPROM, but where erasing can only be done in blocks or the entire chip.

Flip-flop

A digital logic circuit that can be switched back and forth between two states. 

FPGA (Field Programmable Gate Array)

High density PLD containing small logic cells interconnected through a distributed array of programmable switches. This type of architecture produces statistically varying results in performance and functional capacity, but offers high register counts. Programmability typically is via volatile SRAM or one-time-programmable antifuses.

Fuse

A two-terminal device that is normally a low resistive element and is programmed or "blown" resulting in an open or high impedance.

Gate

In electronic circuitry, a pathway that may be open or closed, depending on the source of the input, the strength of a signal, or the conductivity of chemicals used in semiconductors. Logic gates are programmed to correspond to related "if-then" statements. The state of an open or closed gate is analogous to the binary state of a 0 or a 1. The application of this analogy allows computing machinery with millions of gates to respond conditionally and to perform logical functions.

Gate Array

IC that is customized by interconnecting an array of logic elements. Customization is performed by the manufacturer and typically involves non-recurring engineering (NRE) costs and several design iterations.

Glue

Generic term for any interface logic or protocol that connects two component blocks. Hardware designers call anything used to connect large VLSI’s or circuit blocks "glue logic."

Hardware Description Language (HDL)

A kind of language used for the conceptual design of integrated circuits. Examples are VHDL and Verilog. 

IC (Integrated Circuit)

A device in which components such as resistors, capacitors, diodes, and transistors are formed on the surface of a single piece of semiconductor.

In-Circuit Reconfigurable (ICR)

An SRAM-based or similar component which can be dynamically reprogrammed on-the-fly while remaining resident in the system.

In-System Programmable (ISP)

An EEPROM-based, FLASH-based, or similar component which can be reprogrammed while remaining resident on the circuit board.

JEDEC (Joint Electronic Device Engineering Council)

A council which creates, approves, arbitrates, and oversees industry standards for electronic devices. In programmable logic, the term JEDEC refers to a textual file containing information used to program a device. The file format is a JEDEC approved standard and is commonly referred to as a JEDEC file.

JHDL

JHDL is a method of describing (programmatically, in JAVA) the components and connections in a digital logic circuit. More specifically, JHDL provides object classes used to build up circuit structure.

JTAG

Joint Test Action Group (JTAG, or "IEEE Standard 1149.1").

A standard specifying how to control and monitor the pins of compliant devices on a printed circuit board.

Logic

One of the three major classes of ICs in most digital electronic systems: microprocessors, memory, and logic. Logic is used for data manipulation and control functions that require higher speed than a microprocessor can provide.

Logic Function

A mathematical function that performs a digital operation on digital data and returns a digital value.

Logic Gate

The physical implementation of a logic function.

Logic Synthesis

A process in which a program is used to optimize the logic used to implement a design.

Look-Up Table (LUT)

An array or matrix of values that contains data that is searched. An alternative implementation of a CLB; the multiple inputs generate the complex outputs. 

Macrocell

A macrocell on most modern CPLDs contains a sum-of-products combinatorial logic function and an optional flip-flop. The combinatorial logic function typically supports four to sixteen product terms with wide fan in. Thus, a macrocell may have many inputs, but the logic function complexity is limited. On the other hand, most FPGA logic blocks have unlimited complexity, but the logic function only has four inputs.

Netlist

A list of names of symbols or parts and their connection points, which are logically connected in each net of a circuit. A file listing parameters extracted from a circuit schematic.

Noise

The miscellaneous rubbish that gets added to a signal on its journey through a circuit. Noise can be caused by capacitive or inductive coupling, or from externally generated interference.

Non-volatile

The memory elements keep their contents when power is removed from the device. 

Onboard

Contained on the device or on the board.

One Time Programmable

This device can be programmed only once; it's contents can not be changed.  While typically these devices are fuse or antifuse based, they can also be low-cost EPROM devices.  In this case, typically used for production devices, an inexpensive package is used without a window.

Partial Reprogrammability

The ability to leave the internal logic in place and change just one part of the FPGA.

Pinout

A diagram that indicates how wires are terminated to pins in a connector. A list that assigns device functions to specific pins.

Place and Route

Using backend implementation software tools, the process of connecting various memory elements in an FPGA to create a custom logic circuit.

Programmable Logic

A logic element whose function is not restricted to a particular function.  It may be programmed at different points of the life cycle.  At the earliest, it is programmed by the semiconductor vendor (standard cell, gate array), by the designer prior to assembly, or by the user, in circuit.

Programmable Logic Controller

A control device usually used in industrial control applications that employ the hardware architecture of a computer and relay ladder diagram language. Inputs to PLC’s can originate from many sources including sensors and the outputs of other logic devices. Also called "programmable controller".

Reconfigurable Computing

A methodology of using programmable logic devices in a system design such that the hardware-based logic can be changed to perform various tasks. Benefits include the use of fewer components, less power, and the flexibility that bring about. Also allows networked equipment in the field to be upgraded or repaired remotely.

Reprogrammable

These devices can have their configuration loaded more than once.  SRAM-based devices may be reloaded without restriction.  Many other forms of reprogrammable elements have restrictions on the number of write cycles, although they are high enough not to be of practical concern for most applications.  

Rising-Edge

A transition from a logic 0 to a logic 1. Also known as a positive edge.

RTL

Register Transfer Level

Register transfer level description, also called register transfer logic, is a description of a digital electronic circuit in terms of data flow between registers, which store information between clock cycles in a digital circuit. RTL description specifies what and where this information is stored and how it is passed through the circuit during its operation.

Sensor

A transducer that detects a physical quantity and converts it into a form suitable for processing. For example, a microphone is a sensor which detects sound and converts it into a corresponding voltage or current.

SRAM

Static Random Access Memory

A type of memory that is faster and more reliable than the more common DRAM (dynamic RAM). The term static is derived from the fact that it doesn't need to be refreshed like dynamic RAM, but it loses its memory if it's powered off.

Standard Cell

This device differs from the gate array since each cell may be different and optimized for each "standard" function.  There are no standard layers to the device and each layer of the chip is a unique design.

State Machine

The actual implementation (in hardware or software) of a function that can be considered to consist of a set of states through which it sequences.

Switch

A device for making or breaking an electric circuit, or for selecting between multiple circuits.

Synchronous

(1) A signal whose data is not acknowledged or acted upon until the next active edge of a clock signal. (2 )A system whose operation is synchronized by a clock signal.

Trace

A line or "wire" of conductive material – such as copper, silver, or gold – on the surface of or sandwiched inside a PCB, printed circuit board. These traces are often called individually a run. Traces carry an electronic signal or other forms of electron flow from one point to another.

Truth Table

A convenient way to represent the operation of a digital circuit as columns of input values and their corresponding output responses.

Verilog

A Hardware Description Language for electronic design and gate-level simulation. 

VHDL

Very High Speed Integrated Circuit (VHSIC) Hardware Description Language

A Hardware Description Language for electronic design and gate-level simulation. 

Via

Feed-through. A plated through-hole in a printed circuit board used to route a trace vertically in the board, that is, from one layer to another. 

Volatile

The memory elements lose their contents when power is removed from the device.  SRAM-based devices are volatile and require another device to store their configuration program.

 

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Curator: Richard Plastow
NASA Official: Cynthia Calhoun
Last Updated: 02/23/2006