IEEE 1149.7

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IEEE 1149.7

IEEE 1149.7 is complementary superset of the widely adopted IEEE 1149.1 (JTAG) standard that has been in use for more than two decades. IEEE 1149.7 was ratified by the IEEE in Dec 2009. The persistent link to the specification at the IEEE is at

While IEEE 1149.7 adds substantial functionality to the existing standard, it is important to note that it is not a replacement for IEEE 1149.1. Backward compatibility is maintained so that any board or system that integrates chips that support either standard is amenable to test or debug procedures.


The new standard offers embedded designers several benefits, including:

  • The ability to control debug logic power consumption in an industry standard way. Whereas IEEE 1149.1 (JTAG) had a single "always on" state, IEEE 1149.7 offers four selectable power modes to enable ultra-low power devices.
  • The ability to quickly access a specific device in a system with multiple devices. By implementing a system level bypass, the scan chain is drastically shorter, which directly improves the debugging experience.
  • The introduction of a star topology to complement the standard serial topology. Designers working with stacked-die devices, multi-chip modules and plug-in cards will favor the star topology because it simplifies the physical inter-device connections.
  • Two-pin operation instead of the four-pin operation required in IEEE 1149.1. Since most of today's systems integrate multiple ICs and often have severe size constraints, reducing the number of pins and traces will help designers meet their form factor goals and allowing for additional functional pins and/or low package cost.
  • Compatibility with existing IEEE 1149.1 (JTAG) compliant IP, allowing preservation of investment.

Relationship to Other Standards

  • IEEE 1149.1 (JTAG) is the predecessor to IEEE 1149.7.
  • IEEE 1149.6 is focused on boundary-scan testing for advanced digital networks.
  • IEEE 1149.7 is a complementary superset of IEEE 1149.1.
  • IEEE 1500 is a scalable standard architecture for enabling test reuse and integration for embedded cores and associated circuitry.
  • IEEE P1687 is developing a methodology for access to embedded test and debug features, to include a description language.
  • IEEE-ISTO 5001 is the NEXUS debug standard. IEEE 1149.1 is a connection type used by NEXUS. IEEE 1149.7 will be included in the new revision of the NEXUS debug specification.
  • MIPI is the Mobile Industry Processor Interface Alliance, and IEEE 1149.7 is a recommended Test and Debug interface. (see the MIPI T&D White Paper Interface Framework (.pdf))


  • IEEE 1149.7 has been ratified as a standard by the IEEE in Dec 2009.
  • The standard is available from the IEEE.