Control and Operation of the LHCb Readout Boards Using Embedded Microcontrollers and the PVSS II

LHCb is one of the four experiments at the Large Hadron Collider. Before final reconstruction of the data in PC farms, high speed preprocessing is performed on a set of a few hundred custom electronics boards employing large modern field programmable gate array (FPGA) driven electronics. The local control of these boards is achieved via an embedded microcontroller which is connected to a large Local Area Network. After a brief introduction to the hardware we summarize the implementation of the entire layered software architecture for the readout boards and its integration into the Experiment Control System, which is built upon a common control framework based on an industrial SCADA system. Abstraction of different access modes and separation from the modeling of the components in the control system allow the reuse of various components on different hardware types. Each board has several hundreds of registers and memory blocks, so the optimization of write and read accesses is crucial for the start up configuration of the experiment. To facilitate the control of a large number of readout boards, finite state machines are introduced, where the states and transitions are well defined over the whole set of used boards.