A system is provided that includes a memory configured to store test patterns. A first lockstep core and a second lockstep core are configured to receive the same set of test patterns. First scan outputs are generated from the first lockstep core, and second scan outputs are generated from the second lockstep core during a reset of the first lockstep core and the second lockstep core. A comparator can be coupled to the first lockstep core and the second lockstep core and is configured to compare the first scan outputs to the second scan outputs. The first and second lockstep cores can be initialized to a similar state if the first and second scan outputs are the same. The first and second lockstep cores can comprise non-resettable flip flops.

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 circuitry, 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.

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 circuitry, 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.

An implementation of a system disclosed herein includes a decompressor logic with the capability to vary a level of decompression of a scanning input signal based on value of compression program bits and a compressor logic to generate a scanning output signal, the compressor logic including a plurality of XOR logics, wherein the output of the plurality of XOR logics is selected based on the compression program bits.

A chip testing method including the following operations is disclosed: outputting a plurality of testing sequences to a plurality of scan chains by an encoding circuit; generating a plurality of scan output data according to the plurality of testing sequences by the plurality of scan chains; and determining whether an error exists in the plurality of scan chains or not according to the plurality of scan output data by a decoding circuit.

A chip testing circuit and a testing method thereof are provided. The chip testing circuit includes a parameter measurement circuit, a plurality of power supply circuits, a plurality of switch circuits, and a control circuit. The plurality of power supply circuits respectively provide power supply to a plurality of chips carried by a plurality of sockets. Each switch circuit is electrically connected between one socket and one power supply circuit. The control circuit is connected in parallel to a plurality of signal pins of the plurality of chips carried by the plurality of sockets, so that when the control circuit outputs test data, all the chips can simultaneously receive the test data. When executing a parametric test mode, the control circuit controls one of the switch circuits to be turned on and controls the parameter measurement circuit to perform an electrical performance test on the chips.

A chip testing circuit and a testing method thereof are provided. The chip testing circuit includes a parameter measurement circuit, a plurality of power supply circuits, a plurality of switch circuits, and a control circuit. The plurality of power supply circuits respectively provide power supply to a plurality of chips carried by a plurality of sockets. Each switch circuit is electrically connected between one socket and one power supply circuit. The control circuit is connected in parallel to a plurality of signal pins of the plurality of chips carried by the plurality of sockets, so that when the control circuit outputs test data, all the chips can simultaneously receive the test data. When executing a parametric test mode, the control circuit controls one of the switch circuits to be turned on and controls the parameter measurement circuit to perform an electrical performance test on the chips.

A device test architecture and interface is provided to enable efficient testing embedded cores within devices. The test architecture interfaces to standard IEEE 1500 core test wrappers and provides high test data bandwidth to the wrappers from an external tester. The test architecture includes compare circuits that allow for comparison of test response data to be performed within the device. The test architecture further includes a memory for storing the results of the test response comparisons. The test architecture includes a programmable test controller to allow for various test control operations by simply inputting an instruction to the programmable test controller from the external tester. The test architecture includes a selector circuit for selecting a core for testing. Additional features and embodiments of the device test architectures are also disclosed.

A method for testing operation of a device under test (DUT) includes receiving an input bit stream at an input pin, the input bit stream including multiplexed test patterns for a plurality of scan chains of the DUT. The method further includes demultiplexing the multiplexed test patterns, and providing a corresponding test pattern data to each of the plurality of scan chains. The method further includes, at each of the plurality of scan chains, scanning test results from the scan chain, to produce multiplex output test data into an output bit stream.

A circuit comprises a plurality of scan chains configured to perform scan shifting in two opposite directions and a register configured to store a first signal. The first signal determines whether the plurality of scan chains operate in a first mode or a second mode. The plurality of scan chains operating in the first mode is configured to perform, based on a second signal, either scan shifting in a first direction in the two opposite directions or scan capturing during a test; the plurality of scan chains operating in the second mode is configured to perform, based on the second signal, scan shifting in the first direction or a second direction in the two opposite directions.