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Introduction
This chapter introduces you to the basic concepts of Xilinx JTAG
capabilities and the XC9500 series products.
Boundary Scan
What is IEEE 1149.1
Design complexity, difficulty of loaded board testing, and the limited
pin access of surface mount technology led industry leaders to seek
accord on a standard to support the solution of these problems.
Boundary Scan, formally known as IEEE Standard 1149.1, is prima-
rily a testing standard created to alleviate the growing cost of
designing and producing digital systems. The primary benefit of the
standard is the ability to transform extremely difficult printed circuit
board testing problems (that could only be attacked with ad-hoc
testing methods) into well-structured problems that software can
handle easily and swiftly.
The standard defines a hardware architecture and the mechanisms
for its use to solve the aforementioned problems.
What can it be used for
Although primarily a testing standard for on-chip circuitry, the prolif-
eration of the standard has opened to the door to a wide variety of
applications. The standard itself defines instructions that can be used
to perform functional and interconnect tests as well as built-in self
test procedures.
Vendor-specific extensions to the standard have been developed to
allow execution of maintenance and diagnostic applications as well
as programming algorithms for reconfigurable parts. It is the latter
EZTag User Guide
Chapter 1
1-1
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