Method and apparatus for complete functional testing of a complex signal

Abstract

A test register coupled to an absolute delay regulator circuit of a clock repeater chip enables complete functional testing of a clock delay path of the regulator. The test register is connected to a measurement latch of the clock path in a 'logical OR' configuration with respect to a measurement delay line and is enabled during a test mode by control logic of the repeater chip. Operationally, a sequence of logic '0' bits are forced in the measurement delay line during test mode. A state machine clears the measurement latch, and then loads a test pattern into the test register. As each bit of the register is set, a corresponding bit in the measurement latch is also set to simulate a measurement cycle; the results of the 'measurement' are stored in the measurement latch. Once the test pattern is loaded, the repeater chip is placed into a measurement test mode. Execution of a measurement test cycle then propagates the test pattern throughout the clock delay path of the regulator. An output clock signal is sampled and if determined present, indicates that the clock path column under test is functional. Each column of the clock path is then tested separately in sequence.