JTAG boundary scan register bypass register instruction register interface instruction register JTCK signal JTDI signal JTDO signal JTMS signal [1] [2] Tap controller test access port Shift-DR state Update-IR state Capture-DR state interface Shift-DR state Update-DR state JTCK, signal [1] [2] JTDI, signal [1] [2] [3] JTDO, signal [1] [2] JTLB (joint TLB) JTMS, signal [1] [2]