A device comprising: a bus forming a ring path for circulation of one or more data packets around the bus, wherein the one or more data packets comprises a trace report packet for collecting trace data from a plurality of components attached to the bus, wherein the bus is configured to repeatedly circulate the trace report packet with a fixed time period taken for each circulation of the ring path performed by the trace report packet; and the plurality of components, each of which comprises circuitry configured to, upon reception of the trace report packet at the respective component, insert one or more items of the trace data that have been obtained by the respective component.