Patent ID: 8468394

Claim:
A data processing apparatus, said data processing apparatus comprising: a plurality of devices, said plurality of devices comprising: at least one processing unit; and at least one further unit, said at least one further unit comprising: a memory management unit; a direct memory access unit; a bus matrix; a universal asynchronous receiver transmitter (UART) or a slave device; and trace circuitry and tagging circuitry, each of said trace circuitry and said tagging circuitry associated with at least one of said plurality of devices, said tagging circuitry configured to: select at least one item, said at least one item comprising an activity to be monitored; and provide said at least one selected item with tag data identifying said at least one item as an item to be monitored; and said trace circuitry configured to: detect tagged items processed by one of the plurality of devices associated with said trace circuitry other than said at least one of said plurality of devices associated with said tagging circuitry that identified said at least one selected item; and output trace information relating to at least some of said detected tagged items, a plurality of trace sources each associated with a corresponding device, each of said plurality of trace sources operable to detect tagged items and to output trace information relating to at least some of said detected tagged items, wherein said tag data comprises security information of an associated item, said trace source being operable in response to said security information restricting output of trace information to impede output trace information relating to said tagged item and in response to said security information permitting output of said trace information to allow tracing of said trace information.