Abstract: A data processing apparatus and methods are disclosed. The data processing apparatus comprises: data processing elements operable to process data; an energy management unit operable to generate energy management information indicative of an energy state of at least one of the data processing elements when processing said data; and logic operable to receive said energy management information and to generate energy management information items associating said energy state with the processing of said data. The information items can provide visibility of how the Energy State of the data processing elements vary in response to the processing of data. Providing this visibility of the Energy State can advantageously enable more detailed the energy management to be performed and the Energy State of the data processing elements to be optimized.

Abstract: Test access to an integrated circuit 2 is controlled by the use of test access enabling keys. A plurality of different test access enabling levels may be supported corresponding to different keys. The test access control may be performed by dedicated hardware or software executing a secure privilege mode.

Abstract: An integrated circuit 2 including functional circuits 4, 6 and a diagnostic circuit 10 passes a functional signal and a diagnostic signal to/from the integrated circuit using a shared integrated circuit pin 14. The functional signal and the diagnostic signal have relative forms such that they can be simultaneously communicated and respective independent physical communication channels provided therefore. Examples are the diagnostic signal being used to frequency, phase, amplitude or otherwise modulate a functional signal being passed. A diagnostic interface circuit 18 is provided to recover the diagnostic signal from the combined functional and diagnostic signal or to combine the functional and diagnostic signals.