System and method for scan-testing of idle functional units in operating systems

A method of testing an idle functional unit of an operating system comprising:

• Identifying in a system remainder an idle functional unit of the system, the idle functional unit coupled to a processor of the system remainder;
• disabling the idle functional unit and marking the idle functional unit as idle by setting a functional unit idle flag;
• in a test controller, determining the idle functional unit is marked idle and testing the idle functional unit, marking the functional unit as under test in a unit-under-test flag readable by the processor of the system remainder;
• and
• upon completing the step of testing the functional unit, re-enabling the idle functional unit.

A method of testing a system during operation of the system comprising:

• determining that a particular functional unit of the system is idle and setting a functional unit idle flag in an idle unit register;
• selecting a seed and loading the seed into a vector generator;
• determining in a test controller that the functional unit idle flag is set in the idle unit register and marking the functional unit as under test in a unit under test in a functional unit under test flag readable by a processor of the system;
• shifting a vector from the vector generator into a scan chain of the functional unit while shifting a previous state of the functional unit into a state memorizer;
• clocking to capture an output of logic of the functional unit in the scan chain;
• shifting data from the scan chain into the signature generator and generating a signature;
• comparing the signature to an expected signature in a signature memory and generating a fail signal on mismatch;
• restoring the functional unit to the state saved in the state memorizer;
• clearing the functional unit under test flag;
• and
• returning the functional unit to normal operation.