A semiconductor device of the embodiment includes a plurality of scan chains, a shift clock control circuit, and a shift clock generation circuit. The plurality of scan chains each include a plurality of scan flip-flops. The shift clock control circuit outputs, to each of the plurality of scan chains, a control signal that non-inverts or inverts a scan clock signal. The shift clock generation circuit is provided to each of the plurality of scan flip-flops and generates a non-inverted scan clock signal or an inverted scan clock signal based on the control signal, the non-inverted scan clock signal being obtained by non-inverting the scan clock signal, the inverted scan clock signal being obtained by inverting the scan clock signal.

Described herein are integrated circuit chips having test circuitry designed such that independently selectable testing of different power domains using a same scan chain compressor-decompressor circuit may be performed. Also disclosed herein are integrated circuit chips having test circuitry designed such that independently selectable testing of different power domains using multiple different scan chain compressor-decompressor circuits may be performed.

Testing of an electrical device is achieved by providing a test access mechanism within the device that can receive scan frames from an external tester. The received scan frames contain stimulus data to be applied to circuitry within the device to be tested, a command for enabling a test control operation, and a frame marker bit to indicate the end of the scan frame pattern. The inputting of scan frames can occur continuously and simultaneous with a commanded test control operation.

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.

In one embodiment, a device comprises: a first die having disposed thereon a first plurality of latches wherein ones of the first plurality of latches are operatively connected to an adjacent one of the first plurality of latches; and a second die having disposed thereon a second plurality of latches wherein ones of the second plurality of latches are operatively connected to an adjacent one of the second plurality of latches. Each latch of the first plurality of latches on said first die corresponds to a latch in the second plurality of latches on said second die. Each set of corresponding latches are operatively connected. A scan path comprises a closed loop comprising each of said first and second plurality of latches. One of the second plurality of latches is operatively connected to another one of the second plurality of latches via an inverter.

A method for testing a stacked integrated circuit device comprising a first die and a second die, the method comprising: sending from testing logic of the first die, first testing control signals to first testing apparatus on the first die; in response to the first testing control signals, the first testing apparatus running a first one or more tests for testing functional logic or memory of the first die; sending from the testing logic of the first die, second testing control signals to the second die via through silicon vias formed in a substrate of the first die; and in dependence upon the second testing control signals from the first die, running a second one or more tests for testing the stacked integrated circuit device.

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.

A clock control system for a scan chain generates two clock signals. During a shift phase of a testing mode of the scan chain, one clock signal is an inverted version of the other clock signal. The clock control system provides the clock signal and the inverted clock signal to two different scan flip-flops of the scan chain, respectively. Each of the two scan flip-flops performs a flip-flop operation when the received clock signal transitions from a de-asserted state to an asserted state. Thus, the two flip-flop operations are mutually exclusive during the shift phase. As a result, a dynamic voltage drop across the scan chain during the shift phase is reduced.

Test stimulus signals applied to at least one circuit under test are produced in a set of test stimulus generators as a function of test stimulus information loaded in test stimulus registers. Loading of the test stimulus information in the test stimulus registers is controlled as a function of test programming information loaded via a programming interface in a respective control register in a set of control registers. The test stimulus generators are activated as a function of the test programming information loaded in said control registers. Test outcome signals received from the at least one circuit under test are used to produce signature comparison signals, which are compared with respective programmable signature reference signals stored in a set of input signature registers, are produced in response to the signature comparison signals produced from the test outcome signals failing to match with the respective reference signals.

An integrated circuit (IC) can include a plurality of circuit blocks, wherein each circuit block includes design for testability (DFT) circuitry. The DFT circuitry can include a scan interface, wherein each scan interface is uniform with the scan interface of each other circuit block of the plurality of circuit blocks, an embedded deterministic test circuit coupled to the scan interface, wherein the embedded deterministic test circuit couples to circuitry under test, and a scan response analyzer coupled to the scan interface. The scan response analyzer is configured to operate in a selected scan response capture mode selected from a plurality of scan response capture modes. The IC can include a global scan router connected to the scan interfaces of the plurality of circuit blocks. The global scan router is configured to activate a subset of the plurality of circuit blocks in parallel for a scan test.