The Readout Subsystem

The Readout Subsystem

This section describes the SEETFDAQ readout subsystem. In this section you will learn:

• The general structure of the Readout subsystem.
• How to use the control panel for the Readout subsystem.

The Readout subystem is what makes the SEETFDAQ system a data acquisition system. It:

• Manages data taking runs.
• Responds to event triggers, reading out the data associated with the trigger.
• Periodically reads out scaler values.
• Submits data to the remainder of the system, making it available to other components of the system.
• Initiates event recording to disk when appropriate.

subsubsReadout subsystem structurerdosstruct

The structure of the Readout subsystem is shown in the figure below.

For simplicity, the data distribution system has been omitted and event data is shown flowing directly from the Readout program to the EventLog program. The Control Panel application maintains the cohesion of the readout program. Your interactions with this control panel make the system work.

The control panel GUI lets you:

• Start and restart the readout program.
• Begin and end data taking runs.
• Set the title and run number of upcomming data taking runs.
• Produce a "production run", that is a run whose products will be saved when the run exits.

In addition, the control panel autonomously manages you run products in keeping with the directory and file structure defined in http://docs.nscl.msu.edu/daq/overview/standard_nscl_directory_structur.htm.

The control panel also supports user written extensions. A SEETF user written extension ensures that information about the EPICS channels that describe the target and table position are written to file and incorporated amongst the run products for production runs.

The Readout program is, of course, an important component of the Readout subsystem. It:

• Responds to run control command messages sent to it by the Control Panel application.
• At the beginning of a data taking run, it reads the slow controls setting packages and ensures that the V812 CFD and the N568 shaping amplifier are set in accordance with the settings in the current package.
• At the beginning of a data taking run it reads a configuration file that defines the hardware to read and the order in which to read it.
• During a run responds to triggers from the VME hardware and reads out the event that caused the trigger as described by its configuration files.
• During a run periodically reads out scalers that describe the trigger rates in the detectors.

Finally, the EventLog program is run prior to the start of a production run. EventLog produces one of the most imporant products of a run; the event file. The event file contains the data from events that were readout by the Readout program. The format of this file is described online at:

http://docs.nscl.msu.edu/daq/ProductionReadout/Manual/. Scroll the left pane of this document down until you see the link Event data format . Click on that link.

• Operating the Readout Control Panel
• Operational procedures

The Readout Subsystem