1. A method of tracing activity of a data processor comprising the steps of: generating a trace data stream in response to data processor activity in a background mode; stopping data processor operation in response to an emulation halt; operating the data processor to service a real time interrupt received during emulation halt; generating a trace data stream in response to data processor activity in a foreground mode upon a real time interrupt during an emulation halt; and indicating in the trace data stream whether the data processor is in the background mode or the foreground mode.