IEEE 1149.7 (Standard for Reduced-Pin and Enhanced-Functionality Test Access Port and Boundary Scan Architecture) is a superset of the 1149.1 JTAG interface, which, as previously discussed, has been in use since 1990. The IEEE 1149.7 standard (also known in the past as cJTAG or Compact JTAG, and later as aJTAG or Advanced JTAG due to copyright issues with the name CJTAG) was developed to address some of the known limitations of 1149.1 performance and extend its capabilities by creating a complementary standard that addresses the changes in the integrated circuit technology and topology. Originally defined as part the MIPI Test and Bdebug Working Group, 1149.7 defines a hierarchy of new, but JTAG compatible capabilities. With increasing levels of complexity, it replaces the JTAG TAP FSM with alternate TAP.7 architectures to implement additional functionality and maximize debug performance. Like other JTAG extension, a key concern is to maintain backward compatibility with IEEE 1149.1 infrastructure, semiconductor IP, software IP, and existing debug and test tools.