Abstract: A system and method are provided on one or more companion chips having a plurality of cores. Each core has core circuitry and a test interface for carrying out tests in relation to the core circuitry. The test interface has an address register to hold an address of the core and address determination circuitry. The address determination circuitry is configured to compare an address received on an address line to the address held in the address register to determine whether a core is being addressed. The address determination circuitry is also configured to direct the test interface to carry out a testing operation in response to the determination.

Abstract: A system and method are provided on one or more companion chips having a plurality of cores. Each core has core circuitry and a test interface for carrying out tests in relation to the core circuitry. The test interface has an address register to hold an address of the core and address determination circuitry. The address determination circuitry is configured to compare an address received on an address line to the address held in the address register to determine whether a core is being addressed. The address determination circuitry is also configured to direct the test interface to carry out a testing operation in response to the determination.

Abstract: A method of testing a circuit which includes the steps of applying at least one input reference signal to a circuit under test which provides a reference signal from at least one output of the circuit under test, and defining at least one output signal of the circuit with reference to the reference output signal, wherein the timing of the output reference signal is defined independently of the input reference signal.