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Readout and Data Acquisition

The NA44 data acquisition trigger has been described in detail in Section 3.4. Our readout and data acquisition system is described in [36]. NA44 used both CAMAC (Computer Automated Measurement And Control) and VME (Versa Module Eurocard) standards. There were 760 channels read out via CAMAC and a variable number of channels read out via VME C-RAMS (CAEN Readout for Analog Multiplexed Signal). Typically, about 1000 channels were read out per event. The T0, the event scalers, the H2, H3 and H4 TDCs and ADCs, the Cherenkov's counters' ADCs, and the UCAL ADCs were read out via CAMAC. The silicon ADCs, the TIC, and the pad and strip chambers were read out by the VME C-RAMS. After the 1994 run, the C-RAMS were replaced by DRAMS[31]. The speed of the DAQ (data acquisition) was limited by the CAMAC modules, which required about 4 $\mu$s per channel and thus 3 ms per event.

CASCADE[38] (CERN Architecture and System Components for an Adaptable Data acquisition Environment) - a distributed multiple-platform real-time data acquisition system developed at CERN - was chosen as the control software and hardware for the NA44 DAQ.

The DAQ hardware included a VME interrupt module CES RCB 8087 'CORBO', a Fast Intelligent Controller, FIC for short (CES FIC 8234, a Motorola 68040 single processor VME board), an HP-715/80 workstation connected to the FIC via Ethernet, an X-terminal and an STD (Summit Tape Drive) to record the data. The CORBO would accept inputs from the NA44 triggers and the SPS start-of-burst and end-of-burst and transfer them to the FIC via the VME bus. The FIC ran CASCADE event building software under its own OS-9/68K operating system and had 20MB of temporary memory to store the NA44 events during the bursts. Between the bursts, the data would be written to the STD tape. The maximum event rate under normal running conditions was about 120Hz, and the typical size of an event was 5-8 kB. The HP workstation was used as a file server for the FIC, and performed the tasks of run control and event monitoring.