ECO测试系统英文文献和中文翻译(3)
system operating speed.
2. Economics of IC Testing
2.1. Introduction
There are many different test strategies for testing in-
tegrated circuits. These vary from using no structured
DFT approach, relying on good design practice and
experts to generate an effective test, to adopting a single
structured DFT approach [5]. These approaches have
proven valuable and cost effective in many scenarios.
However, whereas one method has proven to be eco-
nomically viable for one company it is not guaranteed
to be so for another. Indeed, what has proven to be
economical for one design might not be economic for
another within the same company.
As the complexity of devices and the variety of struc-
tured partitions of a chip increase there are more and
more DFT approaches that could be used. For example,
in many complex devices an effective test strategy can
be obtained from a mixture of ad hoc methods, struc-
tured DFT and Built-in Self-Test (BIST). This adds to
the complexity and permutations of what can be used.
For example, the number of BIST methods for an
embedded PLA is greater than 20 [6]. Each BIST
method will have a different effect on area overhead,
test length/time, I/O requirement, fault cover, and per-
formance. The relative importance of these character-
istics for each BIST method will change depending on
the PLAfs functionality and size, number of devices to
be tested, and also on the skill of the designer and/or
effectiveness of the design tools. Thus it would be
unreasonable to expect a designer to identify the "best"
test met.hod for each embedded PLA in the design. Fur-
thermore, as we need to minimize the overall design, manufacture, and test costs for the device, our selec-
tion procedure for the "best" DFT method for the
embedded PLA needs to consider what other DFT
methods are being adopted for other partitions of the
device.
2.2. The ECOtest System
The ECOtest System, a tool developed by Brunel
University in collaboration with Siemens-Nixdorf In-
formationssysteme, is a test strategy planning tool utiliz-
ing economics modeling for cost optimal selection of
DFT methods [7]-[10].
The ECOtest System was developed specifically for
the design of ASICs. Chips are fabricated by external
vendors, who also test them with test patterns supplied
by the designers. This definition of the application area
of the test strategy planner affects the design of the cost
model. It thus highlights the specific nature of the
economic results that will be presented later in this ar-
ticle. For example, the fact that an external vendor
fabricates the chips means that the cost of production
can be easily calculated from the vendors prices, if a
good estimation of gate count can be achieved.
The structure of the ECOtest System can be seen
in Figure 2.
The design description is acquired either from the
user or from an existing netlist and is built in a hier-
archical fashion in order to allow test strategy decisions