A circuit comprises: a bit-flipping signal generation device comprising a storage device and configured to generate a bit-flipping signal based on bit-flipping location information, the storage device configured to store the bit-flipping location information for a first number of bits, the bit-flipping location information obtained through a fault simulation process; a pseudo random test pattern generator configured to generate test patterns based on the bit-flipping signal, the pseudo random test pattern generator comprising a register configured to be a linear finite state machine, the register comprising storage elements and bit-flipping devices, each of the bit-flipping devices coupled to one of the storage elements; and scan chains configured to receive the test patterns, wherein the bit-flipping signal causes one of the bit-flipping devices to invert a bit of the register each time a second number of test patterns is being generated by the pseudo random test pattern generator during a test.

A chain of flip-flops is tested by passing a reference signal through the chain. The reference signal is generated from a test pattern that is cyclically fed back at the cadence of a clock signal. The reference signal propagates through the chain of flip-flops at the cadence of the clock signal to output a test signal. A comparison is carried out at the cadence of the clock signal of the test signal and the reference signal, where the reference signal is delayed by a delay time taking into account the number of flip-flops in the chain and the length of the test pattern. An output signal is produced, at the cadence of the clock signal, as a result of the comparison.

A circuit comprises: a bit-flipping signal generation device comprising a storage device and configured to generate a bit-flipping signal based on bit-flipping location information, the storage device configured to store the bit-flipping location information for a first number of bits, the bit-flipping location information obtained through a fault simulation process; a pseudo random test pattern generator configured to generate test patterns based on the bit-flipping signal, the pseudo random test pattern generator comprising a register configured to be a linear finite state machine, the register comprising storage elements and bit-flipping devices, each of the bit-flipping devices coupled to one of the storage elements; and scan chains configured to receive the test patterns, wherein the bit-flipping signal causes one of the bit-flipping devices to invert a bit of the register each time a second number of test patterns is being generated by the pseudo random test pattern generator during a test.

An example one-shot circuit includes: circuitry including a set-reset (SR) latch to produce an output pulse of controlled duration in response to an input signal rising edge, where the SR latch includes a first circuit input and a second circuit input; a circuit path to provide a signal to the first circuit input; and a delay element connected to the circuit path and to the second circuit input.

A chain of flip-flops is tested by passing a reference signal through the chain. The reference signal is generated from a test pattern that is cyclically fed back at the cadence of a clock signal. The reference signal propagates through the chain of flip-flops at the cadence of the clock signal to output a test signal. A comparison is carried out at the cadence of the clock signal of the test signal and the reference signal, where the reference signal is delayed by a delay time taking into account the number of flip-flops in the chain and the length of the test pattern. An output signal is produced, at the cadence of the clock signal, as a result of the comparison.

A sequential circuit includes a data input terminal, a data path, and a redundant feedback loop. The data input terminal receives input data. The data path is connected to the data input terminal and transmits the input data to a data output terminal based on a first clock signal and a second clock signal. The redundant feedback loop is connected to the first data path and stores first data based on at least one of the first or second clock signals when the first data is equal to second data. The first data corresponds to the input data. The second clock signal is a delayed signal of the first clock signal. The second data is delayed data of the first data.

A method and apparatus for forcing equivalent outputs at start-up for replicated sequential circuits is disclosed. An integrated circuit (IC) includes first and second clocked logic circuits each coupled to receive a clock signal common to both, and each configured to produce equivalent logical outputs based on a common set of logic inputs. The IC further includes an equivalence circuit coupled to the outputs of each of the first and second clocked logic circuits. During a system start-up (e.g., power on) and before the clock signal has been applied, the equivalence circuit may detect if the outputs of the to first and second clocked logic circuits originally come up in different states. Responsive to determining that the outputs of the first and second clocked logic circuits are different, the equivalence circuit may cause the outputs to be forced to the same logical state.

A semiconductor chip, a test system, and a method of testing the semiconductor chip. The semiconductor chip includes a pulse generator configured to generate a test pulse in response to a test request; a logic chain comprising a plurality of logic devices serially connected to each other and transferring the test pulse sequentially; and a detector configured to detect a logic level of an output signal of each of the logic devices and output a detection result indicating a degree of an inter-symbol interference (ISI).

A chain of flip-flops is tested by passing a reference signal through the chain. The reference signal is generated from a test pattern that is cyclically fed back at the cadence of a clock signal. The reference signal propagates through the chain of flip-flops at the cadence of the clock signal to output a test signal. A comparison is carried out at the cadence of the clock signal of the test signal and the reference signal, where the reference signal is delayed by a delay time taking into account the number of flip-flops in the chain and the length of the test pattern. An output signal is produced, at the cadence of the clock signal, as a result of the comparison.

A chain of flip-flops is tested by passing a reference signal through the chain. The reference signal is generated from a test pattern that is cyclically fed back at the cadence of a clock signal. The reference signal propagates through the chain of flip-flops at the cadence of the clock signal to output a test signal. A comparison is carried out at the cadence of the clock signal of the test signal and the reference signal, where the reference signal is delayed by a delay time taking into account the number of flip-flops in the chain and the length of the test pattern. An output signal is produced, at the cadence of the clock signal, as a result of the comparison.