Level 1 DAQ System for the KLOE experiment

                Abstract

Both the DAQ slave boards (ADCs, TDCs) and the controllers share the same trigger pulses, incrementing their on-board event number counters. When a trigger occurs, slave boards perform data conversion, label the acquired data with the respective event number, then push the frame in a data queue. Controllers store event numbers in a trigger queue, then proceed to read out the slave boards on a event-by-event basis, retrieving the event number to be processed from the trigger queue.

Level 1 DAQ adopts a modular structure of VME crates tied by a vertical connection. This chain houses up to 8 crates, each with up to 16 slave boards and a local read-out controller - the ROCK. The vertical connection links all the ROCK boards to a chain controller - the ROCK Manager. Ten chains fullfill the KLOE experiment Level 1 DAQ needs.

The ROCK performs crate level read-out, gathering data from slaves on a event number basis. It builds data frames consisting of an event number, slave data and a parity word. In the same fashion, the ROCK Manager performs chain level read-out, collecting the data frame belonging to a given event number from all the ROCK boards.

Both crate and chain level operations rely on custom protocols which have been developed to improve the KLOE Level 1 DAQ performances. At crate level, the AUXbus protocol allows for sparse data scan operations, broadcast transactions and high speed random-length block transfers on a custom backplane. Furthermore, AUXbus protocol carries out cycles labeled by event number, simplyfing event scheduling and data driven behaviour. At chain level, Cbus protocol implements a token-ring architecture with synchronous block transfer capability. It adopts, as physical media, twisted pairs copper cable. Like the AUXbus, the Cbus tags data transactions with event numbers, making the whole chain an event-number-driven machine.

In this paper we describe the ROCK and the ROCK Manager boards we have designed for the Level 1 KLOE DAQ System. We also present the AUXbus and Cbus protocols we have defined for crate and chain read-out. The preliminary version of the two controllers will be shown and their field performances will be briefly discussed.

Submitter`s name: Alberto Aloisio
Submitter`s Institution : Universita` di Napoli "Federico II"
                          and I.N.F.N.- Sez. di Napoli
Address of the Institution: Mostra d`oltremare Pad. 20 80125 Napoli (ITALY)
Submitter`s email address: aloisio@na.infn.it
Submitter's Phone: ++39-81-7253460
            Fax  : ++39-81-2394508
Authors of paper :A.Aloisio(1,2),A.Anastasio(2),S.Cavaliere(1,2),
                  F.Cevenini(1,2),D.della Volpe(1,2),D.J.Fiore(2),L.Merola(1,2)
   (1) : Universita` di Napoli "Federico II" - Dip. di Scienze Fisiche
   (2) : I.N.F.N - Sez. di Napoli
Topic area : (C) DAQ and Triggering