Apparatus for generation of scan control signals for initialization and diagnosis of circuitry in a computer

摘要

A scan testable circuit in a computer system is controlled by using a single scan clock and a fixed delay circuit to realize the required scan clocks and a required scan mode enable signal. The multiple signals are generated from a subset of signals supplied to the scan control signal generation circuit. System data and scan data are routed through a multiplexer to test or initialize lines and circuitry. A scan control signal generation circuit according to the invention has the advantage of eliminating as excess a scan mode enable signal originating elsewhere in the computer system, thereby eliminating unneeded signal traces while minimizing the number of pins required for this function. In a first embodiment, a scan mode enable signal is generated from one of two scan clocks. In a second embodiment, both scan clocks and the scan mode enable signal are generated from a single source clock.