The CERN accelerator control systems access equipment distributed over a geographic area tens of kilometers across.

When off the shelf hardware is not available engineers design and prototype I/O devices as needed. With the advent of the open hardware repository, collaborations between the physics laboratories, research institutes and industry now ensure high quality designs and generality. The manufacture of these devices may be tendered out to industry and the companies involved are free to add them to their own catalogs.

The control system requires very precise timing and synchronization of control and acquisition values over a large area and a diverse array of configurable equipment connected to the accelerators. Great care is required to manage the control system timing and configuration so that remote FPGA cores are set up correctly.

The “White-Rabbit” timing project is open and addresses the future timing and synchronization needs for CERN and other laboratories. White-rabbit makes use of synchronous Ethernet and uses ideas from IEEE 1588 PTP protocol to synchronize remote equipment up to 10Km apart to better than one nanosecond.

Various control system devices at different geographic locations will have on board FPGA logic loaded dynamically by carrier FMC device drivers with configuration data. Device specific drivers then scan the FPGA configuration via a Wishbone-standard bus to determine the installation and if any further configuration is needed.

Etherbone is a software extension of the Wishbone hardware standard permitting remote FPGA cores to communicate with each other and with other control system components.

The variety of I/O peripherals, their wide range of activation mode and the requirement to move several megabytes of data per channel per second is managed by ZIO, a new I/O framework designed to handle the usual I/O channels but also pulse generation and sampling; all peripherals may also be white-rabbit-aware, so that their own timestamps are more precise than what the host computer can offer. Although ZIO examples drive simple I/O channels, the system is able to DMA directly to user space, to sustain high data rates.