Introduction to Boundary Scan
IEEE 1149.1, also known as JTAG or Boundary Scan, was introduced in 1990. This standard endeavors to solve test and diagnostic problems arising from loss of physical access caused by the increasing use of high pin count and BGA devices, multi-layer PCBs, and densely packed circuit board assemblies. The standard outlines predefined protocols for testing and diagnosing manufacturing faults. It also provides a means for On-Board programming of non-volatile memory devices such as Flash, or In-System programming of devices like PLDs and CPLDs.