Boundary-Scan, formally known as IEEE/ANSI Standard 1149.1-1990, is a collection of design rules applied principally at the Integrated Circuit (IC) level that allow software to alleviate the growing cost of designing, producing and testing digital systems. A fundamental benefit of the standard is its 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 easily and swiftly solve. IEEE testing standards of the 1149 family are living entities that grow and change quickly. The Boundary-Scan Handbook, Third Edition is intended to describe these standards in simple English, rather than the strict and pedantic legalese encountered in the standards. Over 180 drawings and 40 tables illustrate important concepts. Forty-six Design-for-Test rules are provided, with complete explanations. The fundamental 1149.1 standard is now over 13 years old and has a large infrastructure of support in the electronics industry. Today, a majority of custom ICs and Programmable Logic Devices have 1149.1 implementations. The Boundary-Scan Handbook, Third Edition updates the information about 1149.1, which has been revised as recently as 2001. It contains a description of the 1149.4 "Analog Boundary-Scan" standard, and gives a tutorial on analog testing technology. It then introduces the recently released IEEE 1149.6 "Advanced I/O" standard, which extends Boundary-Scan to deal with AC-coupled differential signaling now becoming common in higher performance system. Finally, since a board test system provides a suitable environment for programming non-volatile Programmable Logic Devices, the IEEE 1532 standard is described which extends the 1149.1 access protocol into the device programming domain. This forms an essential tool for testing boards and systems of the future.