Generalizing Access to Instrumentation Embedded in a Semiconductor Device

In the 1980s—the early days of circuit boards—most failures were due to poor solder joints on the boards, imperfections among board connections, or problems with the bonds and bond wires from integrated circuit (IC) pads to pin lead frames. The Joint Test Action Group (JTAG) formed in 1985 to provide a pins-out view from one IC pad to another so these faults could be examined. The eventual result was IEEE Standard 1149.1, Test Access Port and Boundary Scan Architecture, last revised in 2013, which defines the test access port (TAP) controller present in all IC chips since Intel released JTAG with its 80486 CPU. JTAG designed the standard to assist with device, board, and system testing; diagnosis; and fault isolation. Today, the term JTAG is used to refer to devices that comply with the standard. Such devices are the primary means of accessing subblocks of ICs, making it an essential mechanism for debugging embedded systems without other debug-capable communications channels. Many years later, another IEEE working group devised the IEEE Standard 1687-2014 for Access and Control of Instrumentation Embedded within a Semiconductor Device—also called internal JTAG, or IJTAG—to bring management, optimization, portability, and scalability to the operation of instruments embedded in semiconductor devices. By instrument, we mean an embedded intellectual property (IP) whose interface would adhere to the rules and Generalizing Access to Instrumentation Embedded in a Semiconductor Device