Patent ID: 8874975

Claim:
A trace unit configured to generate items of trace data indicative of processing activities of a data processing apparatus, said trace unit comprising: a trace input interface for receiving from said data processing apparatus at least one instruction observed indicator indicating execution of a conditional instruction and at least one result output indicator indicating output by said data processing apparatus of a result of executing said at least one conditional instruction; and tracing circuitry for processing said at least one instruction observed indicator and said at least one result output indicator and configured to generate from said at least one instruction observed indicator and said at least one result output indicator corresponding conditional instruction trace data items and conditional result trace data items and to independently output said conditional instruction trace data items and said conditional result trace data items enabling separate trace analysis of conditional instructions and corresponding conditional results by a diagnostic apparatus; wherein said trace unit comprises a result output indicator buffer for storing a plurality of sets of result output indicators received from said data processing apparatus, said trace unit being configured to periodically select a stored set of results for output for processing to said tracing circuitry and in response to one of said instruction observed indicators indicating a conditional instruction referencing a set of result output indicators that said buffer currently store a valid value for, said trace unit is configured to select said currently stored valid set of result output indicators for output such that a new set of result output indicators can be stored.