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What is testing in data compression?
Test compression is a technique used to reduce the time and cost of testing integrated circuits. However, as chips got bigger the ratio of logic to be tested per pin increased dramatically, and the volume of scan test data started causing a significant increase in test time, and required tester memory.
How is data compression calculated?
A algorithm that can take a 2 MB compressed file and decompress it to a 10 MB file has a compression ratio of 10/2 = 5, sometimes written 5:1 (pronounced “five to one”). For example, songs on a CD are uncompressed with a data rate of 16 bits/sample/channel x 2 channels x 44.1 kSamples/s = 1.4 Mbit/s.
What is meant by data compression?
Data compression is the process of encoding, restructuring or otherwise modifying data in order to reduce its size. Fundamentally, it involves re-encoding information using fewer bits than the original representation.
How does scan compression work?
Scan compression relies on breaking the link between the scan I/O and the scan chains such that many more internal scan chains can be constructed making the chain length shorter. The internal scan chains are 4X the number of scan chains in the scan design, hence, the internal scan chains are 4X shorter.
How is DFT compression ratio calculated?
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.
How much data can be compressed?
Data compression can reduce a text file to 50% or a significantly higher percentage of its original size. For data transmission, compression can be performed on the data content or on the entire transmission unit, including header data.
Why test coverage reduces after scan compression?
Scan compression reduces the amount of data needed for digital IC manufacturing tests, thereby lowering the cost of executing patterns on the tester.
What are the standards for a compression test?
CAI requires a drop tower to provide the impact before a compression test is conducted on a testing machine. Most common standards for CAI include Airbus AITM 1.0010, ASTM D 7136D 7137, SACMA 2R-94, and Boeing BSS 7260.
Why is compression testing important for composite materials?
Compression testing is one of the most important tests to determine the behavior of composite materials. Mechanical properties of composite materials can be altered by giving a load to the composite materials, but the properties are difficult to measure directly by a compression test machine.
How is a compressive load introduced into a test?
In general, there are three methods of introducing a compressive load into a test specimen: End loading: all of the load is introduced into the flat end of the test specimen. Shear loading: the load is introduced into the wide faces of the test specimen.
What causes a failure in a compression test?
Buckling is the main failure effect arising during the compression test. Buckling causes the fibers in a material to be opened up or become misaligned, thus breaking the bond between the fibers.