Skip to Main content Skip to Navigation
Poster communications

SPECS: a Serial Protocol for Control System of LHCb

Abstract : The LHCb sub-detector electronics requires a configuration bus able to communicate fast and properly over an up to 120-meter line, with a unique master, and up to 32 slaves located on the detector. In such a configuration, the master card will be located in the control room, which is not exposed to radiation, and the slave close to the detector electronics boards. The slave thus has to be both SEL and SEU immune, in order to work properly in radiation sensitive environments (up to 40Krad of total dose). The SPECS protocol is a 10 Mbit/s serial link designed for the configuration of remote electronics elements. SPECS is a single-master multi-slave bus. The protocol requires 4 lines in BLVDS technology with pole-zero cancellation at the emitter side. The SPECS frame is composed of a fixed-size header (8-bit words which contain information relevant to the transfer), a variable-size data block, and a fixed-size trailer with the checksum of the data block :The SPECS master board will host 4 SPECS masters. This board is implemented on a standard 3.3V 32-bit 33 MHz PCI board. The heart of the system is designed as a portable VERILOG code and integrated within an Altera Cyclone FPGA, the PCI interface being performed by a dedicated circuit (PLX9030). The SPECS slave offers different interfaces: Point to point SPECS interface for long distance interconnections, Multi drop SPECS bus, Local bus parallel interface, 32 configuration I/O lines, JTAG master interface, long distance I2C master bus, 24 commands driver to manage 12 independent links. An intermediate mezzanine board of 0.47dm² houses the SPECS slave, and provides all the described functionalities using 2 SMC connectors. The mezzanine board also provides most of the necessary service functions for the sub-detector front-end electronics. The goal is indeed to avoid putting any unnecessary electronics in the radiation sensitive area.
Complete list of metadata
Contributor : Sabine Starita <>
Submitted on : Monday, August 4, 2008 - 3:36:38 PM
Last modification on : Wednesday, September 16, 2020 - 4:13:40 PM


  • HAL Id : in2p3-00308938, version 1




D. Charlet, D. Breton. SPECS: a Serial Protocol for Control System of LHCb. 2007 IEEE Nuclear Science Symposium and Medical Imaging Conference, Oct 2007, Honolulu, United States. ⟨in2p3-00308938⟩