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IEEE Standard 1149.7: IEEE Standard for Reduced-pin and Enhanced-functionality Test Access Port and Boundary Scan Architecture

Abstract:This specification describes circuitry that may be added to an integrated circuit to provide access to on-chip Test Access Ports (TAPs) specified by IEEE Std 1149.1TM-2001. The circuitry uses IEEE 1149.1-2001 as its foundation, providing complete backward compatibility, while aggressively adding features to support test and applications debug. It defines six classes of 1149.7 Test Access Ports (TAP.7s), T0–T5, with each class providing incremental capability, building on that of the lower level classes. Class T0 provides the behavior specified by 1149.1 from startup when there are multiple on-chip TAPs. Class T1 adds common debug functions and features to minimize power consumption. Class T2 adds operating modes that maximize scan performance. It also provides an optional hot-connection capability to prevent system corruption when a connection is made to a powered system. Class T3 supports operation in either a fourwire Series or Star Scan Topology. Class T4 provides for communication with either a two-pin or four-pin interface. The two-pin operation serializes 1149.1 transactions and provides for higher Test Clock rates. Class T5 adds the ability to perform data transfers concurrent with scan, supports utilization of functions other than scan, and provides control of TAP.7 pins to custom debug technologies in a manner that ensures current and future interoperability.

Status: This standard was ratified by the IEEE in Dec 2009.

Keywords: 1149.1, 1149.7, 2-pin, 2-wire, 4-pin, 4-wire, Advanced Protocol, Advanced Protocol Unit, APU, Background Data Transfer, background data transport, BDX, boundary scan, BSDL, BSDL.1, BSDL.7, BYPASS, Capture-IR, CDX, Chip-Level TAP Controller, CID, Class T0, Class T1, Class T2, Class T3, Class T4, Class T5, CLTAPC, compact JTAG, compliant behavior, compliant operation, control level, controller address, Controller ID, Controller Identification Number, CP, Custom Data Transfer, custom data transport, Data Register, debug interface, debug logic, debug and test interface, DOT1, DOT7, DTI, DTS, DTT, Debug Test System, debug test target, Escape, EOT, EPU, extended operation, Extended Protocol, EXTEST, HSDL, HSDL.7, IDCODE, Instruction Register, JScan, JScan0, JScan1, JScan2, JScan3, JTAG, MScan, MTCP, Multi-TAP Control Path, narrow Star Scan Topology, nTRST, nTRST_PD, optimized scan, OScan, OScan0, OScan1, OScan2, OScan3, OScan4, OScan5, OScan6, OScan7, 1149.1, 1149.7, Pause-DR, Pause-IR, PC0, PC1, RSU, Reset and selection unit, RTI, Run-Test/Idle, scan, scan DR, scan format, scan IR, Scan Packet, scan path, scan performance, scan protocol, scan topology, series, Series Branch, Series Scan, Series Scan Topology, Series-Equivalent Scan, Series Topology, Shift-DR, Shift-IR, SiP, Star Scan, Star Scan Topology, Star Topology, Star-2, Star-2 Branch, Star-2 Scan, Star-2, Scan Topology, Star-4, Star-4 Branch, Star-4 Scan, Star-4 Scan Topology, SP, SScan, SScan0, SScan1, SScan2, SScan3, stall, SSD, Scan Selection Directive, Standard Protocol, star scan, STL, System Test Logic, TAP, TAP controller, TAP controller address, TAP selection, TAP.1, TAP.7, TAP.7, TAPC, TCA, TCKC, TDI, TDIC, TDOC, TDOE, Test Access Port, test and debug, Test-Logic-Reset, TLR, TMSC, Transport Packet, T0, T0 TAP.7, T1, T1 TAP.7, T2, T2 TAP.7, T3, T3 TAP.7, T4, T4 TAP.7, T4(N), T4(N) TAP.7, T4(W), T4(W) TAP.7, T5, T5 TAP.7, T5(N), T5(N) TAP.7, T5(W), T5(W) TAP.7, TP, Update-DR, Update-IR, ZBS, zero bit scan

Related Standards:

IEEE 1149.1:

Copyright ©2007 IEEE-SA
(Stephen Lau (
(Modified: Today's Date)