Embedded controllers for local board-control

The LHCb experiment at CERN has a large number of custom electronics boards performing high-speed data processing. Like in any large experiment the control and monitoring of these crate-mounted boards must be integrated into the overall control-system. Traditionally this has been done by using buses like VME on the back-plane of the crates. LHCb has chosen to equip every board with an embedded microcontroller and connecting them in a large local area network. The intelligence of these devices allows complex (soft) real-time control and monitoring, required for modern powerful FPGA driven electronics. Moreover each board has its own, isolated control access path, which increases the robustness of the entire system. The system is now in pre-production at several sites and goes into full production during next year. The hardware and software are discussed and experiences from the R&D and pre-production are reviewed, with an emphasis on advantages and difficulties of this approach to board-control