The Hall A data acquisition uses CODA (CEBAF Online Data Acquisition), a toolkit developed at Jefferson Lab by the Data Acquisition Group. For general information about CODA, see www.jlab.org/#<6646#>heyes.
We have one fastbus crate in the electron spectrometer and two fastbus crates in the hadron spectrometer. The fastbus modules are of the following types: (1) LeCroy model 1877 TDCs operating in common-stop with 0.5 nsec resolution for our drift chambers and straw chambers; (2) model 1875 TDCs operating in common-start with 0.1 nsec resolution for our scintillators and trigger diagnostics; and (3) model 1881M ADCs for signals from scintillators, Cerenkov, and leadglass detectors. Event-driven readout of our beam position monitors and raster current is available from VME systems.
The trigger supervisor is a custom-made module built by the data acquisition group. Its functions are to synchronize the readout crates, to administer the deadtime logic of the entire system, and to prescale various trigger inputs. We have two trigger supervisors, one in each spectrometer. This allows us to run the spectrometers independently if needed.
Use the public account ``adev'' for running runcontrol, and use ``adaq'' for other online software including ESPACE. On ``adaq'' the directory tree of an experiment is adaq/$EXPERIMENT which is organized in subdirectories of various tasks, such as scaler display, ESPACE, and other online codes, all of which will be described in sections below. The trigger management software is described in the Trigger chapter.