Using scan technology for debug and diagnostics in a workstation environment

An architecture for implementing scan technology for test and debug in a state-of-the-art workstation is described. Architectural features include controlling the scan and clock functions from a single resource which can also perform linear-feedback shift-register-based pseudorandom testing and test-result compression by signature capture. Operations of the scan subsystem are controlled from a service processor which uses a diagnostics bus to communicate with individual scan and clock resource units present on each system board. For debug purposes the service processor has been linked with a remote computer and software has been developed to display and/or modify system state variables (flip-flops). Analysis of scan overhead indicate that benefits in test and debug of the target system far outweigh the cost of implementing scan technology for the APOLLO DN 10000 workstation