What is launch on shift and launch on capture?
The launch-on-shift-capture (launch-on-capture-shift) test is a three-pattern test for transition faults that launches transitions by both launch-on-shift and launch-on-capture mechanisms. The concepts of LOSC and LOCS tests and their signal waveforms are illustrated in Fig.
What is the difference between LOS and LOC?
At-speed scan-testing method is further classified into two types namely, Launch-Off-Shift (LOS) and Launch-Off-Capture (LOC). LOC, a scheme mostly used to abate the test power consumption, is also known as broad-side test scheme, while LOS scheme used to improve transition fault coverage.
What is Atspeed?
At-speed clocks
An at-speed test clock is required to deliver timing for at-speed tests. There are two main sources for the at-speed test clocks. One is the external ATE and the other is on-chip clocks. Traditionally, ATE has always supplied the test clocks.
How do you reduce pattern count in ATPG?
One way to reduce pattern count through increased efficiency of DFT is to use a hybrid ATPG/logic built-in self-test (LBIST) method. This technique has gained increased adoption among automotive IC designers. The once-separate ATPG and LBIST technologies have merged so the scan compression IP can also apply BIST tests.
What is launch on capture?
In launch-off-capture (LOC) method the transition is launched and captured through the functional pin (D) of any flip-flop in the scan chain. Since, the launch pattern V2 depends on the functional response of the initialization vector V1, the launch path is less controllable due to which the test coverage is low.
What is DFT compression ratio?
If your uncompressed design has 10 scan chains with 10 scan channels, then the compression ratio is 1:1. If you add compression so the number of internal scan chains is 100, then the compression ratio is now 10:1 or 10x.
What is test mode in DFT?
The first input of the multiplexer is the functional reset as before. The second input is the DFT (test) controlled RESET and the select line (test mode) is used by DFT to switch to the controlled reset in test mode.
What is LOC and LOS in DFT?
LAUNCH ON CAPTURE (LOC) and LAUNCH
ON SHIFT (LOS) Main transition fault ATPG methodologies are Launch on Capture and Launch on Shift (also known as broadside-load and skewed-load respectively). They both launch transition at the input of combinational block in different way for the same fault detection.
What is Atspeed testing in VLSI?
At-speed scan test involves loading scan chains at a slow clock rate and then applying two clock pulses at the functional frequency. If the circuit is operational, then the transition will propagate to the end of the path in time and the correct value will be captured.
What is ATPG in DFT?
ATPG (acronym for both Automatic Test Pattern Generation and Automatic Test Pattern Generator) is an electronic design automation method/technology used to find an input (or test) sequence that, when applied to a digital circuit, enables automatic test equipment to distinguish between the correct circuit behavior and …
What is test compression in DFT?
What Is Scan Compression and How Can It Help? Scan compression is the most commonly used design-for-test (DFT) architecture for reducing ATPG test application time and test data volume. A traditional compression structure is made up of three distinct blocks: a decompressor, a compressor, and an X-tolerance or X-mask.
What is wrapper in DFT?
A wrapper is a thin shell around the core, that provides the switching between functional, and core-internal and core-external test modes. Together with a test access mechanism (TAM), the core test wrapper forms the test access infrastructure to embedded reusable cores.
What is OCC in DFT?
On-chip Clock Controllers (OCC) are also known as Scan Clock Controllers (SCC). OCC is the logic inserted on the SOC for controlling clocks during silicon testing on ATE (Automatic test Equipment).
What is at speed in DFT?
Why is ATPG needed?
What are ATPG modes?
Description. ATPG (Automatic Test Pattern Generation and Automatic Test Pattern Generator) is an EDA method/technology used to find an input or test sequence.
Why EDT is used DFT?
EDT (Embedded deterministic testing) is employed in order to reduce the test volume and reduced ATE memory usage due to large number of test patterns. This paper aims to determine, how well the EDT architecture performs in a DFT environment in terms of coverage for atspeed and stuck at fault model.
What is Intest and Extest?
EXTEST checks the physical connections of the boundary-scan device. INTEST and RUNBIST test the internal logic of the device. Manufacturer-defined tests might require you to preset the cells in the boundary register (PRELOAD) so the states will be known when the test mode is entered.
Why are wrapper cells used in DFT?
The wrapper cells do not provide isolation but are treated like internal scan chains of the core, and the wrapper cells on input and output are transparent as in functional mode. This mode helps to test paths through the core I/Os while keeping all the core scan chains (including wrapper scan chains) intact.
What is OCC and PLL?
Abstract—In this paper, an on-chip clock (OCC) controller with bypass function based on an internal phase-locked loop (PLL) is designed to test the faults in system on chip (SOC), such as the transition-delay faults and the stuck-at faults.
What is clock mixing in DFT?
Majorly, in DFT, we avoid mixing different clocks in the same chain, but if there is a constraint to I/O ports we have to stitch scan flops driven by two different clocks in one chain.
What is TDL in DFT?
TDL is the industry standard tool for accurate test vector translation, compression, validation and visualization. You can use it to convert your DFT patterns, functional simulation or Scan ATPG, to ATE patterns.
Which algorithm is used for ATPG?
Roth’s D-Algorithm (D-ALG) defined the calculus and algorithms for ATPG using D-cubes. Goel’s PODEM used path propagation constraints to limit the ATPG search space and introduced backtrace.
How can you tell if a fault is stuck?
After obtaining the test vectors for grounded pins, each pin is connected in turn to a logic one and another set of test vectors is used to find faults occurring under these conditions. Each of these faults is called a single stuck-at-0 (s-a-0) or a single stuck-at-1 (s-a-1) fault, respectively.