1. An apparatus comprising: a data bus network interface module for enabling reception and transmission of application messages to/from at least one host processing module of an integrated digital signal processing device via a data bus network; the data bus network interface module being arranged to receive at least one data bus message from at least one remote network node via the data bus network, read a non-data field of the received at least one data bus message, and make data content of the received at least one data bus message available to at least one debug module if the non-data field comprises a value defined for debug use.