What is JTAG boundary-scan?

JTAG/boundary-scan (IEEE Std 1149.1) is an electronic four port serial JTAG interface that allows access to the special embedded logic on a great many of today’s ICs (chips) . The JTAG accessible logic interface serves a number of functions that can include any or all of the following:

• Test logic that enables testing of connections between devices without external probes;
• Programming logic in Flash memories, CPLD’s and FPGA’s for on-board programming of these devices;
• Debug logic in microprocessors and microcontrollers used for software debugging, or to test connections with peripheral devices at speed without embedded software, or to program the embedded flash in a microcontroller.

Devices with a JTAG/boundary-scan interface and logic, are present on many of today’s Printed Circuit Board Assemblies (PCBA’s). The devices are often connected in serial (daisy chain) formation, to form a so-called ‘scan chain’ on the PCBA. An external JTAG/boundary-scan controller is used to activate the logic and complete the testing of the board and programming of devices. Using the JTAG/boundary-scan logic minimizes the amount and complexity of equipment for testing boards and for device programming in design, manufacturing and service as it removes the need for external probing and complex fixtures.

In summary JTAG/boundary-scan saves time and costs for your board test and programming systems and more important of course also on a corporate level.