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ABIST - 1) A form of memory BIST (Built in Self Test)
for embedded memories. 2) A form of BIST targeted at testing analog circuits.
AC Scan - Form of scan test application, where only the sample interval
is required at the specified operating frequency in order to verify timing
performance, as well as structural content. The scan data may be shifted
at a different frequency (typically slower). AC scan allows slower testers
to be utilized and does not place unnecessary constraints on the design
to be able to shift at-speed.
active filter - An electronic filter that combines active circuit
devices, usually operational amplifiers, with resistors and capacitors.
Typically, active filters more closely match ideal filters than passive
active load - A programmable circuit that acts as a pullup or pulldown
load when connected to a DUT pin.
active test site - An operational test site that has its tester
channel numbers present in the test-programs pinlists. A multisite device
test starts with all operational sites active. If a device fails, its
site is deactivated.
algorithm - A set of rules with a finite number of steps for solving
Aliasing - There are a number of different kinds of aliasing that
can occur in BIST engines. The most commonly discussed type of aliasing
occurs when two faults have a canceling effect in the signature register.
In other words, two wrongs appear to make a right. Two other forms of
aliasing are zeroing and overcounting the LFSR. Zeroing refers to the
occurrence of a zero in the LFSR that can have a reset-like effect on
the LFSR and 'erase' the history of the previous tests. Overcounting occurs
when a value or sequence in the LFSR occurs more than once in a test,
typically due to a roll-over (e.g. 1 + 2n cycles of an n-bit counter will
guarantee that at least one value will be repeated). Overcounting can
generate a similar test history 'erasing' phenomenon.
alias frequency- A false lower-frequency component that appears
in analog data that is reconstructed from original data digitized at an
insufficiently high sampling rate.
ambient level - The values of signals and noise that exist at a
test location when the device under test is not active.
amplitude modulation - The process in which the amplitude of a
carrier wave is varied according to a specific law.
analog-to-digital conversion - The process that changes an analog
signal into a digital magnitude value.
analog-to-digital converter (ADC or A/D converter) - An electronic
circuit that produces a digital output directly proportional to an analog
anechoic chamber - An enclosure especially designed with walls that
absorb sound or radiation, creating an essentially free-field environment
antenna - A device that radiates or receives electromagnetic waves.
anti-alias filter - A filter that attenuates noise and high-frequency
components of an analog signal prior to its conversion into a digital
APG - Tester resource that generates vectors on-the-fly, programmatically
(algorithmically) , usually for memory test.
area analysis - An image-analysis technique that finds the area in
an image that falls within a range of specific gray levels.
argument - A value or address passed to a function at the time of
call; also referred to as actual parameter.
array - An ordered arrangement of information.
aspect ratio - The width-to-height ratio of a video picture.
assembler - A program that translates mnemonics into binary codes
that run on a computer.
asynchronous - An action that takes place at an arbitrary time, without
synchronization to a reference timer or clock.
asynchronous transfer mode (ATM) - A fast-packet switching technology
that uses asynchronous time-division multiplexing.
ATE - Automatic Test Equipment. An automated, usually computer-driven, approach to testing semiconductors, electronic circuits, and printed circuit board assemblies.
ATPG - Tool-based approach to test pattern or program development
that relies heavily on the design database. DFT and ATPG go hand-in-hand.
At-Speed Scan - Form of scan where both the data shift and sample
occur at the rated frequency of operation. Structure and timing performance
can both be verified with this kind of scan test.
attenuation - The difference in a signal's voltage, current, or power
from when the signal is transmitted to when it is received.
autorange - The change of the measurement range by an automatic
instrument so it can report with best accuracy a quantity at its input.
averaging - Mathematically smoothing the results of several measurements
by adding them and dividing by the number of samples.
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background - In a personal computer, programmed operations that take
place without direct operator intervention; for example, network operations,
display refreshing. See also foreground.
balun - An antenna-balancing device that matches a balanced or
symmetrical load (a dipole antenna) to an unbalanced load (a coaxial-cable
feed line). ("Balun" is derived from "balanced-to-unbalanced.")
band-pass filter - A filter that passes only those signal frequencies
between two set frequencies.
bandwidth (BW) - A range of frequencies over which a system works
without degrading the original signal.
baseband - In video and audio transmissions, a signal that is unmodulated.
BILBO - A BILBO is a multitalented logic circuit that can be a state
register, a scan register, an LFSR, or a MISR depending on the state of
it's mode pins. BILBOs are sometimes used to cascade large combinational
logic blocks in a BIST engine.
bipolar - (1) A signal that includes positive and negative values.
(2) A type of semiconductor.
BIST - (Built in Self Test) BIST essentially builds tiny tester models
onto the integrated circuit so that it can test itself.
bit map - A set of values that specify colors or gray levels in an image.
blob - A connected region in an image in which all pixels have the
same gray level.
blooming - Saturation of light-sensing elements in a TV camera. Blooming
causes clipping at the camera's maximum brightness level.
Boundary Scan - Generic term for IEEE 1149.1. It is a methodology allowing
complete controllability and observability of the boundary (I/O) pins via
a standard interface. (AKA JTAG)
brightness - The value associated with a pixel that represents a gray
value between black and white.
broadband emission - An emission that has a spectral energy distribution
that is sufficiently broad, uniform, and continuous to ensure that a measuring
response does not vary significantly when tuned over a given frequency
butterfly - A basic math operation that forms part of a fast Fourier
transform algorithm. Memory test pattern.
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catastrophic fault - These are faults such as open and short circuits
that cause sudden and large variation in component values.
channel - The tester functions and the path through a pin-group card
and DUT fixture dedicated to one DUT pin.
characterization test - A series of tests designed to determine the
operating regions and reliability of a device under varied operating conditions.
checksum - The sum of a group of data values. Usually transmitted
with the data to assist in error detection.
chrominance - The color part of a video signal that defines the hue
and saturation, but not the brightness or luminance, of the signal.
clamp voltage - A fixed voltage coupled by a diode or its equivalent
to limit the voltage excursion of a transition or a current supply.
codec - An abbreviation of coder-decoder; a device that can encode
and decode information.
cold-junction compensation - An artificial reference level that compensates
for ambient temperature variations in thermocouple circuits.
color bars - Standard test pattern on a display screen of fully saturated
colors (red, green, blue, magenta, cyan, and yellow) plus black and white.
common-mode rejection ratio (CMRR) - A measure of an instrument's
ability to ignore or reject interference from a signal that is common
to the instrument's input terminals, but relative to ground. (Expressed
comparator - A circuit whose output is a digital logic level that
depends on whether its input signal is above or below a threshold at a
specified time interval.
compare - To apply functional data to a comparator and obtain the
compiler - A program that translates high-level-language statements
into codes that a computer can execute.
compliance voltage - The voltage range a current source or sink can
produce within its constant current specifications.
composite sync - A video signal that contains horizontal-sync pulses,
vertical-sync pulses, and equalizing pulses only, with a no-signal reference
composite video- A signal composed of luminance (black and white),chrominance
(color), blanking pulses, sync pulses, and a color-burst signal.
Concurrent Test - Performing different tests simultaneously to one or
more devices. For instance, you might be testing different BIST circuits
simultaneously on the same chip. Alternatively, you might be testing different
BIST circuits simultaneously on different chips.
Cone of Logic - The combinational logic in a circuit that resolves to
a single observe point.
conducted emission - Electromagnetic energy that is propagated along
a conductor. This energy is called "conducted interference" if
it is undesired.
contrast - A measure of brightness content in an image. High contrast
implies mainly dark-black and bright-white content; low contrast implies
a small spread of gray values.
conversion time - The time required from the moment a channel is interrogated
to the moment that accurate data is available. Usually associated with
DACs and ADCs.
convolution - The integration of the product of two functions in
time. Convolution in the time domain is equivalent to multiplication in
the frequency domain.
coprocessor - A processor that operates with the CPU to boost speed.
For example, a digital signal processing (DSP) chip can free the CPU from
having to perform repetitious math operations.
counter (1) - In software, a memory location used to store a count
of certain occurrences. (2) In hardware, a circuit that counts events.
See also event counter.
counterpoise - The reference-plane portion (grounded or ungrounded)
of an unbalanced antenna.
cross assembler - A program that runs on one computer and generates
instructions for another type of computer.
cross coupling - The coupling of a signal from one channel, circuit,
or conductor to another, where it becomes an undesired signal.
cross modulation - Modulation of a desired signal by an undesired
signal. This is a special case of inter modulation. See also inter modulation.
crosstalk - A phenomenon in which one or more signals interfere with
current loop - A communications method that transmits data as current
flow over relatively long distances and through environments with relatively
CUT - See DUT.
cycle time - The time duration from the start of one cycle to the start
of the next.
cyclic redundancy check (CRC) - A mathematically generated number
that data receivers use to verify the proper bit arrangement in a bit
Cyclization - The process by which discrete time signals (such as supplied
in VCD) are mapped to a representation amenable to automatic test equipment.
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data acquisition (DAQ) - Gathering information from sources such as
sensors and transducers.
data collection - The collection of selected information in a file
during a specified operation.
data logging - The recording of selected information during a specified
operation, such as data recorded during a device-test run.
data reduction - The transformation of raw data, such as that logged
during a device-test run, to human-usable forms, such as graphical representations
DBT - (Defect Based Test) Test development philosophy (mind set) that
begins by looking at the fab's defect densities, the circuit layout and
the creating test sets that will uncover the defects most likely to affect
the device defect levels. In contrast with more conventional methodologies,
which strive to get the highest possible fault coverage, without regards
to their impact on yields and defect levels.
DC Scan - Form of scan where shifting and sampling occurs well below
the devices normal operating frequency. This type of scan is effective for
a 'pure' structural approach (i.e. for stuck-at faults) and, in general,
timing performance cannot necessarily be verified with this type of scan.
debugger - A process used for test-program development, device characterization,
incoming inspection, and production-floor trouble shooting.
decibel (dB) - A logarithmic measure of the ratio of two signal levels:
dB = 20 log (Voltage1 / Voltage2) dB = 10 log (Power1 / Power2)Variants
on the decibel (dB) used in spectrum-analysis and network-analysis measurements
are dBmV absolute voltage level referred to 1 mVdBµV absolute voltage
level referred to 1 µVdBm absolute power level referred to 1 mWdBc
level difference referred to a carrier level, c. dBc/Hz level difference
referred to carrier level calculated for a measurement bandwidth of 1
Hz. (Spectrum and network analysis.)
decoupling-network - An electrical circuit that prevents test signals
that are applied to the unit under test from affecting other devices,
equipment, or systems that are not under test.
Defect(s) - Term used to reference specific flaw(s); physical or chemical
imperfection, on a manufactured device. Most defects can be detected and
measured by a Failure Analysis group. Specific devices that do not perform
as expected contain defect(s) or have Design flaws.
Defect level - The fraction of devices shipped, which can be expected
to be defective (ie. escapes) due to incomplete test coverage. Usually expressed
as a percentage number. See DPM.
degradation - An unwanted change in the performance of a system undergoing
testing. A degradation is not necessarily a malfunction or failure.
design rules - Allowable dimensions used in the layout and design
of an integrated circuit. Such rules are specific to different types of
Detectability - The degree to which it is possible, within the constraints
of test equipment, to observe faulty output behavior of a faulty component.
In other words,
detectability is the minimum deviation that pushes the component out of
the tolerance range.
detectability - A given fault is detectable if a test stimulus
measures a difference within a nominal response.
DFM - Design For Manufacturing. Term used to define activities done
during the design process (by Designers) to ensure that the design is optimized
for the Fab Process that will create the product.
DFT - (Design For Test) Design For Test is the practice of adding hardware
hooks to integrated circuits in order to facilitate effective, inexpensive
diagnostic tests - Tests intended to determine the cause of a possible
malfunction and to suggest a repair strategy.
die - A piece of semiconductor with circuitry fabricated on it; one
location on a wafer; compare chip.
digital-to-analog conversion - The process that changes discrete values
into a voltage or current.
digital-to-analog converter (DAC or D/A converter) - A device that
converts digital information into a corresponding analog voltage or current.
dipole - An antenna made of a straight conductor (usually not longer
than half a wavelength) that is divided at its electrical center and connected
to a transmission line.
direct memory access ( also see DMA) - The direct transfer of information
between a computer's memory and a device while the computer's CPU does something
discrete cosine transform - A mathematical operation that compresses
video data in JPEG and MPEG files.
DMA - (Direct Memory Access) With respect to test, DMA refers to an
architecture that allows direct addressability and observability of embedded
DPM - The defect level expressed as defective parts per million units.
driver - Software that controls a specific hardware device, such as
a data-acquisition board or a printer.
driver - The circuitry that adds voltage levels to input signals and
applies the results to a DUT pin.
DUT - Device Under Test ( pronounced "dut") This is the target
device being tested. Less frequently referred to as "CUT" (circuit
DUT fixture - A circuit board that interfaces the test head to a device-under-test
(DUT) socket, a probe card, or a connector for a device handler. It has
mate with the pogo pins on the pin-group cards in the test head and includes
power terminals, signal lines
dynamic range - The ratio of the full-scale range (FSR) of a data
converter to the smallest difference the converter can resolve. (Dynamic
range is generally expressed in decibels. )
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EDA - electronic design automation. EDA refers to the design tools
and environment utilized to render the logic, schematics, insert scan, insert
BIST, etc. for a new chip design.
edge - An abrupt voltage or current change.
edge detection - A technique that locates an edge by examining an
image for abrupt changes in pixel values. See also image processing.
edge-placement accuracy - The precision within which an edge can be
placed relative to a reference.
electromagnetic compatibility (EMC) - (1) The ability of electronic
equipment to operate in an intended electromagnetic environment without
degradation caused by interference. (2) The ability of equipment to operate
in its electromagnetic environment without creating interference with
error - A discrepancy between an expected value and a measured value.
error capture - The collection of a specified group of functional
vectors upon detection of a functional error.
event counter - A circuit that counts the occurrences of a certain
condition. See also counter.
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false color - Color added to an image to call attention to details
that aren't readily perceptible or to create special effects.
false reject- When thresholds are tighter than they need to be, fault-free
circuits can be rejected because they fall outside of narrowly defined
limits for nominal value.
far field - The region in which the power flux density from an antenna
obeys the inverse-square law. For a dipole antenna, distances beyond l/2
are far-field regions.
false accept - When faulty circuits operate within test thresholds,
a test program can pass them when they should in fact be rejected. False
acceptance happens when fault occurs within the upper threshold of faulty
Fault(s) - This term is used in reference to classes, or concepts, of
defect types. The most common of these is the stuck at type, or fault class.
In the EDA and academic worlds, a fault is a software model of a defect,
or class of defects.
Fault Coverage - Quality measure for a test or set of tests, based on
the percentage of actually detected faults (defects) versus the total number
of theoretically detectable faults, on a particular fault model. A coverage
figure should be given for each model type tested. As the operator defines
the nodes to be evaluated (in some cases this is done by defining lists
of nodes not to be used in the task) the raw number has little meaning without
a full analysis of the set up.
fault dictionary - A fault dictionary contains the same information
contained in a fault list, but include information about how the fault manifests
itself including the error location and its effect on circuit components.
It may also include suggested test conditions.
fault dominance - Dominance is the condition in which the deviation
at the output caused by one fault is negligible compare with the deviation
at the same output, but caused by a different fault.
fault equivalence - Two faults are said to be equivalent if their
effects on the output cannot be distinguished from each other.
fault list- A fault list that contains every possible fault for consideration,
but no information bout how the fault manifests itself under various circuit
conditions and test conditions.
fault masking - Two faults are said to be mask each other if their
sensitivities are equal and opposite in sign.
feature - In inspection, any characteristic of an image or a region
in an image.
feature extraction - A technique that generates a set of descriptors
or characteristic attributes from a binary image.
field (1) - The set of either the even or odd lines in an interlaced
video image. The concept of a field is used when dealing with an interlaced
video display. (2) A large open site at which testing can take place.
field of view - The area of the object under view as represented at
the focal plane of a camera.
field strength - The measurement of either the electric field or the
magnetic field that is made in the far field. (Expressed in units of V/m,
A/m, or W/m.)
file name - Part of the identification used to locate a file on a
file transfer protocol (FTP) - A protocol that transfers files over
filter - An operation that selectively removes noise from a signal.
Electronic filters include low-pass, band-pass, and high-pass types. Mathematical
filters can operate on data to extract information and to enhance images.
firewall - Hardware or software that protects a network from un authorized
firmware - A program permanently recorded in ROM; it is effectively
a piece of hardware that performs software functions.
flaw detection - An image-analysis technique that examines an object
for unwanted features of unknown shapes at unknown positions.
force - To stimulate DUT pins with formatted pattern data.
foreground - In a personal computer, the activity subject to direct
operator intervention. Background activities may be running on the computer
format - To produce a waveform from pattern data and timing information
in accordance with a format mode.
frame - In inspection, the total area of the picture that is scanned
by a camera.
frame grabber- A device that digitizes an image and stores it in a
frame rate - The frequency at which an image is completely updated
on a display monitor.
frame relay - A technology for transmitting data packets in high-speed
bursts across a digital network.
Full Scan - Scan architecture (implementation) where all of the memory
elements (flip-flops) are scannable in the design.
functional perturbation - At the output of a functional macro (for example,
a sub-circuit such as an amplifier), functional perturbation represents
the deviation of the output from its nominal value due to a soft or hard
functional preconditioning - Setting a logic device (for example,
a counter) to a desired state by applying stimulus (sequencing through
functional test vectors) and checking output until the desired state is
reached. Also called match mode or loop-until-pass.
functional test - A process that applies pattern vectors to a device
and checks the output to determine that the device is operating according
to its truth table.
Functional Testing - Also known as behavioral testing. Strategy of testing
integrated circuits that focuses on the expected functionality of the circuit.
Defects are targeted in an indirect way. The test methodology closely parallels
the application space of the circuit being tested.
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genlock - Extraction of horizontal-sync and vertical-sync signals
from a video signal and the use of those signals to synchronize video
Global System for Mobile Communications (GSM) - A pan-European standard
for digital cellular radio. Originally known as Groupe Spéciale
go/no-go test - A test with minimum and maximum limits that stops
on the first error without performing any diagnostics, characterization,
or actual measurements other than limit checking.
gray level - The brightness value assigned to a pixel; values range
from black, through gray, to white.
gray scale - The discrete gray levels that are defined for an imaging
system or imaging software. In an eight-bit system, the gray scale runs
from 0 to255.
ground - (1) An electrically neutral wire that has the same potential
as the surrounding earth. Normally, a non-current-carrying circuit intended
for safety. (2) A common reference point for an electrical system.
ground plane - A conducting surface or plate used as a common electrical
reference point for circuits.
guard band - 1. (device testing) Adjustment made to a DUTs test
specification to take into account test-system accuracy, repeatability,
reproducibility, and correlation.
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hard fault - A hard fault is a potential open or short circuit in
the design modeling the effects of manufacturing defects on the network
harmonic distortion (HD) - A form of distortion in analog circuits
that generates harmonics (signals whose frequencies are integer multiples
of the input signal). It is calculated as the ratio of a single harmonic
to the level of the original signal. Harmonic distortion is related to
total harmonic distortion (THD), the ratio of the sum of multiple harmonics
to the level of the original signal.
hexadecimal - The base-16 numbering system; 0_9, A_F.
hexadecimal notation - The representation of numbers in the positional
number system with base 16. The sixteen hexadecimal digits are usually
represented by 0-9, A-F.
high-pass filter - (1) A math operation that emphasizes details in
an image. (2) A circuit that attenuates low-frequency components in an
hipot - high-potential
Histogram - In inspection, the graphical representation of the gray-scale
values found in an image.
horizontal blanking - The blanking signal that occurs at the end of
each video scanning line.
horizontal sync - The portion of a video signal that indicates the
end of a line of video information.
Hue - The distinction between colors. Red, blue, green, and yellow
are examples of hues. White, black, and gray are not considered hues because
they are intensities, not colors.
hypertext transfer protocol (http) - The protocol that negotiates
document delivery to a Web browser from a Web server.
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IDDQ - Quiescent Supply Current (IDD). Theoretically, static CMOS
logic should have nearly zero current when the clock is stopped. This methodology
puts the chip into various logic states, stops the clock and measures the
power supply current.
I/O address - A specific hardware circuit and software value that the
CPU uses to distinguish between the different boards in a system.
I/O channel - An input/output tester port that is capable of both
stimulating a device pin and monitoring a response from the same pin.
image analysis- A technique that extracts features and descriptions
image processing - Transforming a source image into an improved image
that supplies specific properties. For example, edge detection is an image-processing
immunity - The property of a piece of equipment that enables it to
reject an electrical disturbance.
Impulse - An electromagnetic pulse of short duration shorter than
one cycle at the highest frequency being considered.
inhibit - To turn off a driver, placing it in a state that approximates
an open circuit.
Input isolation - Any mechanism for isolating a core's inputs from the
surrounding circuitry, such that the core completely ignores these inputs.
This may be useful while testing the surrounding circuitry to prevent unintentional
behavior in the cores not being tested.
instrumentation amplifier (IA) - An amplifier circuit with high-impedance
differential inputs and high common-mode rejection.
intermodulation - The mixing of two signals in a nonlinear device.
This produces signals at frequencies that are the sum and difference of
integral multiples of the original signals. See also cross modulation.
Interpreter - A program that translates high-level-language instructions
,one at a time, into computer code. The computer runs the resulting code
as soon as the interpreter translates individual instructions. Examples
include dialects of Basic.
interrupt - A signal that requires immediate attention from a computer's
interrupt handler - The software routine that handles an interrupt's
request for service.
interrupt vector - A type of interrupt that immediately points a computer
to a new series of instructions. See also interrupt.
isolation amplifier - An amplifier that provides electrically isolated
inputs and outputs that let it amplify a differential signal that is superimposed
on a high common-
isolation voltage - The voltage that an isolated circuit can normally
withstand. Isolation voltage is specified from input to input or from
any input to the amplifier output.
isotropic - Having properties that have equal value in all directions.
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Java - A subset of the C++ language specifically meant for running
applications on the Web.
JTAG - (Joint Test Action Group - pronounced "jay-tag") Originally,
the name of the team, through a not uncommon twist of fate, the term has
come to be associated with the output of the team. JTAG is now essentially
synonymous with the IEEE 1149.1 standard for Test Access Port and Boundary
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laser - light amplification by stimulated emission of radiation
LBIST - (Logic Built In Self Test - pronounced "L bist") A
form of BIST targeted at testing random logic. Typically, this is done with
PRPGs feeding scan logic and the outputs are connected to a MISRs. All commercial
forms of LBIST require a full scan infrastructure.
LFSR - (Linear Feedback Shift Register) LFSRs are shift registers with
exclusive-OR gates that allow some bits in the register (usually referred
to as a polynomial) to feed back into selected points within the register.
LFSRs are often used in BISTed designs to form PRPGs and MISRs.
library - A collection of routines, data, or other material in a file
from which a user can draw for use in a project such as a test program.
line - In imaging, the coordinate that defines the vertical location
of a pixel in an image.
linearity - The relationship of a device's response to a straight
link - 1. (scan) The data fed to a scan pin on one scan clock cycle
Ñ the scan equivalent of a parallel vector.
lot - (device production context) A group of semiconductor devices,
usually from the same production run, treated as a unit.
low-pass filter - (1) An operation that blurs details in an image.
(2) A circuit that attenuates the high-frequency components in an analog
LSSD - (Level Sensitive Scan Design) Type of scan design that uses master/slave
latches which have different clock phases to isolate each scan node.
luminance - The brightness or intensity of a color.
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macro - A set of program steps combined by a user or a programmer
that act as a single and more powerful program step.
mask - To set a comparator state used to ignore the result of a comparison.
MBIST - (Memory Built In Self Test - pronounced "M bist")
BIST approach that is specific to memory testing.
memory module- The memory module, of which there may be two per board,
contains either 18 M or 72 M of memory. This memory can be used for DBM,
ECR or Vector testing.
mismatch - A non ideal coupling of two circuits. The part of the signal
that does not pass through the coupling gets reflected and leads to measurement
MISR - (Multiple Input Shift Register - pronounced "miser")
Also known as Multiple Input Signature Register. MISRs are simply LFSRs
configured as signature analyzers. MISRs are often used on the back end
of BIST engines to capture and compress output sequences from a circuit
monochrome - An image represented by a single color. Generally, a monochrome
image is presented as white on a black background.
monopole - An antenna that consists of a straight conductor and is
usually not more than one quarter of a wavelength long. A monopole is
mounted immediately above, and at a right angle to, a ground plane.
monotonicity - A characteristic of a properly operating DAC in which
the analog output increases as the digital code input to it increases.
multidie probing - Using probes on several dice on a wafer to conduct
a parallel test of more than one die at a time.
multiplexer (MUX) - A set of semiconductor or electromechanical switches
arranged to select one of many inputs to a single output.
multisite - Refers to more than one test site on a single test head.
multisite testing - Using a single test program and a single test
head with more than one test site to test more than one device either
in parallel or in sequence. The sequential test of two or more devices
is called a ping-pong test.
Mux-D - Type of scan design that uses D type flip-flops with input
multiplexers to isolate each scan node. This is the most widely used type
of scan element.
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noise - Undesirable electrical interference to a signal.
noise distortion - The nonlinear behavior that circuits or devices
exhibit when driven with a broadband noise signal.
noise floor - (1) The level below which no information can be obtained
from a signal. A signal that occurs below a noise floor is permanently
lost. (2)The minimum discernible signal that can be detected by a receiver.
non-observable fault - A fault is considered non-observable if its
effects cannot be measured at any network output.
NTSC (National Television System Committee) - A 60-Hz standard for
encoding color video signals. The standard is used in North America, Canada,
Japan, and most of South America. See also PAL, RS-170.
Nyquist sampling theorem - A theorem that states that if you sample
a signal at rate f, the sampled signal will contain no information about
signals with frequency components above f/2.
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open area - An open and flat test site at which electromagnetic-interference
measurements are taken and at which effects from power wires, buildings,
and underground cables are negligible. Ambient radiation must be low enough
to permit testing.
operational test sites - Test sites on a multisite test head declared
on to the test program. This assures that a test site is usableÑno
broken socket, channel runs exist. An operator can declare test sites
optical isolator - A device that links two circuits through an optoelectronic
transmitter and receiver with no direct electrical connection between
the two circuits.
Output isolation - Any mechanism for isolating a core's outputs from
the surrounding circuitry, such that the surrounding circuitry may be tested
without contention from the cores not under test.
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P1500 - Emerging IEEE standard for test wrappers (common -scan like
test structures "wrapped around SOC cores).
PAL - (phase alternation line) A 50-Hz composite color video standard
used in Western Europe, India, China, and some Middle Eastern countries.
Seealso NTSC, RS-170.
palette - The range of colors that a display can produce.
Parallel Test - Testing more than one device simultaneously. By convention,
this is usually assumed to be identical tests on identical devices. (contrast
to Concurrent Test).
parameter - A quantity in a function (or subroutine), or at a device
port, the value of which is selected according to circumstances. Parameters
are distinguished from variables, recorded measurements, constants, and
fixed values. A formal parameter is one defined
parameter file - A data set containing the voltage, current and timing
information for a specified test on a particular device.
parametric faults - These faults are caused by variations in component
parameter values produced by process or environmental changes.
parametric test - The measurement and verification of terminal voltage
and current characteristics at a device pin.
Partial Scan - Scan architecture (implementation) where only some
of the storage elements (flip-flops) are scannable.
passive filter - A filter circuit using only passive components such
as resistors, capacitors, and inductors.
Path Delay - Fault characterized by a particular logic path being
too slow to meet the overall timing requirements of a circuit.
pattern - The binary data applied to and expected from a DUT during
a functional test.
pattern vector - The pattern data applied to and expected from a DUT
during one test cycle.
PC Card - The name of version 3.0 of the PCMCIA form factor.
pinlist - An array of pin-name/channel-number pairs.
pitch - The center-to-center distance between adjacent leads on a
device or package.
pixel - (1) The fundamental picture element in a digital image. (2)
The coordinate unit used to define the horizontal location of a pixel
in an image. ("Pixel" is an acronym for "picture element.")
pogo pin - A kind of spring-loaded pin formed of two small tubular
sections joined together with an internal spring and with a contactor
formed on the end of the smaller tube; used to contact pads on a circuit
polarization - The orientation of the field vector in a radiated field.
polling - A round-robin canvassing of inputs to a computer to determine
which ones are active. In most cases, polling is synchronized in software
to a clock or external trigger.
Port - A communications connection on a computer or a remote controller.
For example, an I/O port.
programmable logic levels The signal and reference voltage levels applied
to the driver and comparator rails.
Primary Input - Physical input from the outside world to a device,
can be a signal input, a scan chain input, etc. (Note: In the case of
cores in an SOC, the outside world may still be inside the chip).
Primary Output - Physical output to the outside world from a device,
can be a signal output, a scan chain output, etc. (Note: In the case of
cores in an SOC, the outside world may still be inside the chip).
PRPG - (Pseudo- Random Pattern Generator) PRPGs are LFSRs that
are sometimes used on the front end of BIST engines to generate pseudo-random
patterns to be presented to a circuit under test.
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quantizing error - The inherent uncertainty in digitizing an analog
value that is caused by the finite resolution of the conversion process.
Increasing the resolution of an ADC reduces the uncertainty.
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radio-frequency interference (RFI) - High-frequency interference with
range - (1) The maximum and minimum allowable full-scale signal (input
or output) that yields a specified performance level.
region of interest - In inspection, the area inside defined boundaries
of an image that you want to analyze.
repeatability - The ability of an instrument to give the same output
or reading under repeated identical conditions.
resolution - The smallest division to which a measurement can be determined.
For example, an ADC with 12-bit resolution can resolve 1 part in 4096
(212) over its input range.
RGB (red-green-blue) - A video-display standard in which three separate
signals red, green, and blue transmit image information.
RS-170 - The encoding standard for 60-Hz black-and-white television
signals; it is used as the standard for most monochrome video equipment.
See also NTSC, PAL.
RS-343 - Similar to RS-170, but this encoding standard provides high-resolution
color information for computer video applications.
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sample and hold (S/H) - A circuit that acquires an analog voltage
and stores it temporarily in a capacitor. This circuit is also referred
to as a sample-and-hold amplifier (SHA).
Scan - DFT technique where traditional functional logic is reconfigured
into "chains" for direct test access to internal nodes.
Scan Chain - Serial organization of scan elements such that the first
element of the chain is at a device input and the last element of the chain
is at a device output. Devices may use single or multiple scan chains to
'capture' all of the scannable nodes.
SECAM - sequential color and memory, a video standard used in China,
Russia, and France.
Seebeck effect - The principle that describes how thermocouples work.
A thermocouple circuit contains two junctions of two dissimilar metals.
sensitivity - A measure of the minimum change in an input signal that
an instrument can detect.
settling time - The time required, after rapidly changing a circuit's
input signal, for that circuit's output voltage to settle and remain within
a specified error band around the final value.
SFDR - spurious-free dynamic range
Shadow Logic - User defined logic (UDL) accessible only from the input/output
ports of an embedded core (i.e.. IP). The core is said to cast a shadow
which potentially reduces the testability of the logic in that shadow. The
addition of test access to the core's ports is said to cast light on or
remove the shadow.
shmoo plot - A graph of pass/fail test results that plots pairs of
test criteria such as frequency vs. voltage, or voltage vs. temperature.
The shapes of such plots may resemble (roughly) the ghost-like Shmoo character
introduced to the Li'l Abner cartoon strip by Al Capp in the 1940s.
shmoo plot - A one-axis or two-axis pass/fail plot of a series of
measurements corresponding to plot coordinates, thus showing the operating
region for a device for those parameters.
shutdown - The (usually graceful) termination of operation-system
execution on a processor (or system of processors).
signal-to-noise ratio (SNR) - The ratio of total signal to noise expressed
in decibels (dB). The larger the number, the better. SNR is calculated
by SNR = 20 log (SignalRMS / NoiseRMS)A related unit is the signal-to-noise-and-distortion
ratio (SINAD), the ratio of the input signal to the sum of noise and harmonics:
SINAD = 20 log (SignalRMS / (Noise + Harmonics)RMS)simultaneous sample
and hold= A data-acquisition technique in which several sample-and-hold
circuits sample several different analog channels simultaneously.
sink current (active load) - Conventional current flow into a DUT
with the active load as pull-up.
sink voltage (active load) - Terminal voltage at a DUT acting as current
Site - When discussing parallel test, a site refers to the logical partitioning
of tester resources for each device. When discussing a fault, or defect,
the physical location on the chip where the fault or defect lies.
site - A DUT position on a test head with more than one such position.
site number - A number that identifies a site location on the test
skew - The effect of different propagation delays between signal origins
and device pins (or other points, for example, probes).
skew- Any observed difference in time between two events that occur
SOC - (System on a Chip) Practice of integrating one or more processor
cores, embedded memories, peripheral interfaces, and sometimes mixed signal
circuits onto a single chip to form a complete (or nearly complete) system.
soft fault (parametric fault) - Any fault caused by a parametric
or process variation outside of tolerance or nominal values is called a
source current (active load) - Conventional current flow out of a
DUT with the active load as pull-down.
source voltage (active load) - Terminal voltage at a DUT acting as
spike - A transient disturbance of an electrical circuit caused by,
for example, load variations on the AC power line.
spooler - A process that queues jobs for background printing (or other
SRSG - (Shift Register Sequence Generator) A simple PRPG (single output)
- defined here because it's used in the definition of STUMPS.
stability - The ability of an instrument or sensor to maintain a consistent
output when a constant input is applied.
STDF - (Standard Test Data Format) STDF is a standard output format
for test results. There are numerous tools for post processing STDF generated
files and performing statistical analysis on a population of tested devices.
STIL - (Standard Test Interface Language - pronounced "style")
STIL is an emerging standard for test development. It is supported as an
output format by the ATPGs of most EDA toolsets. None of the ATEs currently
support STIL directly, however because STIL is richer in capabilities than
WGL, the industry trend is toward full STIL support. Some testers may eventually
support STIL as their native test language.
Stimulus - An input signal which imitates action or reaction in a
circuit, such as voltage or current.
strobe - A signal that clocks a logic state into a latch or D flip
flop. In a semiconductor test, an edge strobe records a comparison result
at a specified instant in the cycle; a window strobe records any error
occurring during a timed interval.
Structural Testing - Strategy of testing integrated circuits that focuses
on detecting manufacturing defects. Unlike functional or behavioral testing,
defects are targeted directly.
STUMPS - (Self Test Using MISR and Parallel SRSG - pronounced "stumps")
STUMPS is a common BIST architecture that combines a PRPG (or multiple SRSGs),
multiple scan chains, and a MISR.
subpixel resolution - Any imaging technique that can yield a measurement
with a spatial resolution of less than one pixel.
successive-approximation - A technique used in ADCs that sequentially
compares a series of progressively smaller binary-weighted values with
an analog input to produce an output digital word.
Surge - A sudden change (usually an increase) in the voltage on a
powerline. A surge is similar to a spike, but it lasts longer.
susceptibility - The characteristic of electronic equipment that permits
undesirable responses when the equipment is subjected to electromagnetic
sync - The portion of a video signal that indicates either the end
of a field or a line of video information.
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TAP - (Test Access Port - pronounced "tap") Part of the
JTAG standard, the TAP is a 4 (or optionally 5) pin port to enable boundary
Test protocol - A sequence of control operations required to perform
a test. At the lowest level a test protocol is just a series of logic 0
and 1 applied to specified test control ports. It will typically also contain
symbolic references to the test data that is to be applied to or observed
at specified test data or system data ports. Test protocols involve the
activation of one or more test modes and may also contain pre-conditioning
and post-conditioning functions or sequences.
test specification - A document defining the operational parameters
of a device.
test vector - A test vector or test setup condition is a set of stimuli
applied to the device-under-test (DUT) to elicit a known output at a given
test measurement node.
tester - An assembly of apparatus used for evaluating semiconductor
throughput rate - The maximum repetitive rate at which a data-conversion
system can operate with a specified accuracy.
time stamp - Information added to a unit of data to indicate the time
at which it was processed.
time-out - An error event that occurs after a maximum time interval
for an expected event.
tolerance - Tolerance is the deviation allowed for a component ( for
example, R,C,gm,Cgs,etc. ) of its measured output, such as voltage magnitude.
For component variation, tolerance is the deviation of an element with
respect to its nominal value.
total harmonic distortion (THD) - See harmonic distortion.
trace - To monitor the execution of a program and report the sequence
of actions carried out.
Transition Delay - Fault characterized by a particular gate or gate
connection being too slow-to-rise or too slow-to-fall to meet the overall
timing requirements of a circuit.
tristate -A high-impedance third state for a device output.
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UDL - (User Defined Logic) Special purpose logic added by the SOC chip
integrator (e.g. not a purchased IP), for use as "glue" logic,
or part of the system chip product differentiator.
uniform resource locator (URL) - The name (or string of characters)
that uniquely identifies each Web site. For example, www. tmworld.com.
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Validation - A "post-silicon" process to prove (with evidence)
a design to be valid. For our purposes, validation is any use of special
purpose test hardware to prove the product meets the design intent; as opposed
to other usage of the same equipment as a manufacturing screen.
VCD - (Verilog Change Dump) Output from Verilog used for pattern
generation. Typically this output has to be translated into a format that
is readable by a tester. This translation process is typically performed
by several third party and in-house tools.
vector - 1. A parallel vector is the functional logic applied to
a DUT during one clock cycle.
Verification - A "pre-silicon" process done during development,
for gaining confidence, that a Design will produce a pre-defined result.
An output of verification may be translated into ATE vectors (used for functional
vertical sync - The portion of a video signal that indicates the
end of a field of video information. This sync pulse is used by video equipment
to maintain field synchronization with the incoming video signal.
video encoder - A device that converts RGB video to composite video.
voltage-to-frequency converter (VFC) - A device that converts an analog
input voltage into a sequence of digital pulses with a frequency that
is proportional to the input voltage.
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wafer - A thin, polished slice of monolithic semiconductor on which
an array of die are fabricated.
wafer map - A plot of the viable dice on a wafer showing pass/fail
information, parameter variation, or some other characteristic.
waveform - The succession of signal levels applied to the DUT pin
after combining pattern and timing information.
WGL - (Waveform Generation Language - pronounced "wiggle")
WGL is the de-facto standard for ATPG and vector generation. Most pattern
development tools support WGL and there are third party tools that specialize
in the conversion of WGL to various tester native vector formats.
WLBI - (Wafer Level Burn In) Wafer Level Burn In is a manufacturing
technique where a particular product is burned in as full wafers to take
advantage of massive parallelism and higher temperature acceleration factors.
Wrap I/O - DFT technique where a pin's output is wrapped back
in to it's input (or the input of another pin). This can allow some testing
of pins that are not contacted directly by the tester. Note: This definition
actually does the concept a disservice, because Wrap I/O is really much,
much more - though beyond the scope of this glossary.
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X.25 - A CCIT standard that describes how a switched-packet network
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yield - The proportion of good devices in a lot or run.
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