A method of loading a data string into a Joint Test Action Group (JTAG) shift register is provided. The method includes determining whether the last bit of the data string is equal to one or zero. In response to determining that the last bit is equal to one, the method includes simultaneously setting each flip-flop of the shift register to one, identifying first data string loading bits by removing, from the data string, the last bit and any other bits in a continuous sequence of bits, including the last bit, that are each equal to one, and sequentially loading the identified first data string loading bits into the shift register. A testing apparatus for performing the method and an enhanced JTAG interface are also provided. The method, testing apparatus, and enchanced JTAG interface may reduce the number of clock cycles required to load the shift register.

Testing of die on wafer is achieved by; (1) providing a tester with the capability of externally communicating JTAG test signals using simultaneously bidirectional transceiver circuitry, (2) providing die on wafer with the capability of externally communicating JTAG test signals using simultaneously bidirectional transceiver circuity, and (3) providing a connectivity mechanism between the bidirectional transceiver circuitry's of the tester and a selected group or all of the die on wafer for communication of the JTAG signals.

This disclosure describes die test architectures that can be implemented in a first, middle and last die of a die stack. The die test architectures are mainly the same, but for the exceptions mentioned in this disclosure.

The first logic wafer is attached to a supporting wafer, which adds sufficient depth to this bonded structure such that the first logic wafer may be thinned during the manufacturing process. The first logic wafer is thinned such that the through silicon vias may be etched in the substrate of the first logic wafer so as to provide adequate connectivity to a second logic wafer, which is bonded to the first logic wafer. The second logic wafer adds sufficient depth to this bonded structure to allow the supporting wafer to then be thinned to enable through silicon vias to be added to the supporting wafer so as to provide appropriate connectivity for the entire stacked structure. The thinned supporting wafer is retained in the finished stacked wafer structure and may comprise additional components (e.g. capacitors) supporting the operation of the processing circuitry in the logic wafers.

This disclosure provides methods and apparatuses for testing a tested circuit. In an implementation, a chip test circuit transmits input data of a test vector to a data distribution circuit through an input of a test bus, and transmits the input data of the test vector to a scan input channel of a tested circuit through the data distribution circuit. After scanning of the tested circuit ends, output data of the test vector of the scan output channel of the tested circuit is transmitted to an output of the test bus through the data distribution circuit to complete the test of the tested circuit. A dynamic correspondence between the data distribution circuit and the test bus is implemented by configuring a first selector, so that test resources can be dynamically allocated.

A test circuit transmits input data of a test vector to a data distribution circuit using an input of a test bus, and transmits the input data of the test vector to a scan input channel in a circuit under test using the data distribution circuit. After scan of the circuit under test is completed, output data of the test vector on a scan output channel in the circuit under test is transmitted to an output of the test bus using the data distribution circuit, to complete testing of the circuit under test. A dynamic correspondence between the data distribution circuit and the test bus may be configured based on a specific test solution, so that a test resource can be dynamically allocated.

In some examples, an integrated circuit comprises: a TDI input, a TDO output, a TCK input and a TMS input; a TAP state machine (TSM) having an input coupled to the TCK input, an input coupled to the TMS input, an instruction register control output, a TSM data register control (DRC) output, and a TSM state output; an instruction register having an input coupled to the TDI input, an output coupled to the TDO output, and a control input coupled to the instruction register control output of the TAP state machine; router circuitry including a TSM DRC input coupled to the TSM DRC output, a control DRC input coupled to the TSM state output, and a router DRC output; and a data register having an input coupled to the TDI input, an output coupled to the TDO output, and a data register DRC input coupled to the router DRC output.

An Integrated Circuit (IC) includes a storage element and control circuitry. The control circuitry is configured to select, responsively to a scan-enable control, between a functional-data input and a scan-data input to serve as an input to the storage element, to selectively disable toggling of an output of the storage element, responsively to a clock-enable control, by gating a clock signal provided to the storage element, and, while the clock-enable control indicates that the output of the storage element is to be disabled from toggling, to select the input of the storage element to be the scan-data input.

A scan chain architecture with lowered power consumption comprises a multiplexer selecting between a functional input and a test input. The output of the multiplexer is coupled to a low threshold voltage latch and, in test mode, to a standard threshold voltage latch. The low threshold voltage latch and standard threshold voltage latch are configured to store data when a clock input falls, using a master latch functional clock M_F_CLK, master latch test clock M_T_CLK, slave latch functional clock S_F_CLK, and slave latch test clock S_T_CLK. The slave latch has lower power consumption than the master latch.

The disclosure provides a novel method and apparatus for inputting addresses to devices to select the device TAP for access. Further, the disclosure provides a novel method and apparatus for inputting addresses for selecting device TAPs and for inputting commands for commanding circuitry within the device. The inputting of addresses or the inputting of addresses and commands is initiated by a control bit input on TDI that is recognized during the Run Test/Idle, Pause-DR or Pause-IR TAP states.