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.
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.
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.
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).
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.