A modem device for use in a wireless communications terminal comprises a plurality of functional units to perform signal processing tasks which are connected in a ring structure. Each of the functional units comprises a local processor, a plurality of hardware accelerators and a switching matrix connected between a data input of the respective functional unit and each of the sub-components. The local processor receives task instructions from a controller of the modem device over a first bus system that uses a first protocol which includes addressing, and in response to the task instructions configures the hardware accelerators and switches the switching matrix to selectively produce connections between the data input and the hardware accelerators in a manner to perform the intended task. Data flow occurs in a ring structure between said functional units and through each of the functional units using a second protocol without addressing.