Data Acquisition Software System

Electronics

The data acquistion electronics is based around CAMAC using camac set-up and control with an ECL bus (fera or fera-like) data readout.

The CAMAC crates use Kinetic Systems RS232 crate controllers. The system currently supports up to 8 CAMAC crates although only 4 or 5 are normally used.

Amplifiers developed for Megha are computer controlled and interfaced to the data acquisition system using multi-drop RS485. Currently 10 crates of amplifiers are in-use each containing 32 amplifiers (a total of 320 channels).

The ECL bus data readout is interfaced to the data acquisition processor via a VME module (F2VB – fera to VME bus). This module provides a 2 Mbyte dual port memory buffer and also marks the received data stream with end-event tags.

# Data Acquisition Processor

The data acquisition processor is a Motorola MVME2431 single width VME board module. This contains a PowerPC 750 microprocessor running at 350 MHz with 32 Mbyte SDRAM, on-board fast Ethernet controller and 64 bit VME interface. The LynxOS real time software kernel is used (release 3.0.1).

A Green Spring VME bus Industry Pack carrier with RS232 and RS485 IPs provides the interface to the CAMAC and Megha amplifiers mentioned above.

The F2VB is accessed via the VME bus and all other communication is via ethernet.

LynxOS is a UNIX like system enhanced for real-time use. The OS is initially booted from a Sun workstation (charissa1) but once the data acquisition software components are loaded and running no further access to the Sun is required unless additional software components are required by manual intervention.

# Experiment Control

All components of the data acquisition software system are controlled and monitored via MIDAS. Normally this will be a session running in charissa1 but any of the workstations can be used if needed.

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# Data Acquisition Server

This is a Sun workstation (normally charissa1) which acts as the boot server for the data acquisition processor and runs the MIDAS Tape Server program.

The data read from the F2VB by the data acquisition processor is transmitted via Ethernet to the Data Acquisition Server where the Tape Server program writes it to tape (normally DLT).

# Online Data Analysis

The read-out program running in the data analysis processor performs simple checks on the data, generates statistics and builds “singles” histograms for each adc. Online data analysis is performed by Sunsort which is given access to the event data in real time by a “spy” program watching the Ethernet data traffic between the data acquisition processor and the tape server program.

Sunsort can be run in this mode in any of the Sun workstations.