BORA: A front end board, with local intelligence, for the RICH detector of the Compass collaboration

In this paper we describe the design of the re-configurable front-end boards (BORA boards) for the 82944 channel RICH-1 (Ring Imaging CHerenkov) of the Compass Collaboration (NA58). The front-end electronics controls the sample-and-hold operation after the arrival of an event trigger, acquires the analog voltages from the pre-amp VLSI and converts them into 10 bits at a rate of 20 Ms/s per analog channel. The digitized analogue values are then written into FIFOs. A subsequent operation compares the readings of each and every channel with corresponding programmable thresholds, and transmits those values larger than the threshold, together with the channel number, through an optical fiber to subsequent processing stages of the acquisition system. The overall operation of the board is controlled and supervised by a fast DSP. The availability of local intelligence allows the board to present innovative features such as: to be part of a computer network that connects several similar boards of the detector with a PC. The presence of the DSP allows testing the operability and linearity of the analog channels; and creating engineering frames containing local temperatures and voltages and transmitting the results through the network. The operator can reconfigure the hardware and software of the board by downloading programs from the PC.