Communication between Trigger／DAQ and DCS in ATLAS

Within the ATLAS experiment Trigger/DAQ and DCS are both logically and physically separated.Nevertheless there is a need to communicate.The initial problem definition and analysis suggested three subsystems the Trigger/DAQ DCS Communication (DDC) project should support the ability to :1.exchange data between Trigger/DAQ and DCS;2.send alarm messages from DCS to Trigger/DAQ;3.issue commands to DCS from Trigger/DAQ.Each subsystem is developed and implemented independently using a common software infrastructure.Among the various subsystems of the ATLAS Trigger/DAQ the Online is responsible for the control and configuration.It is the glue connecting the different systems such as data flow.level 1 and high-level triggers.The DDC uses the various Online components as an interface point on the Trigger/DAQ side with the PVSS II SCADA system on the DCS side and addresses issues such as partitioning,time stamps,event numbers,hierarchy,authorization and security,PVSS II is a commercial product chosen by CERN to be the SCADA system for all LHC experiments,Its API provides full access to its database,which is sufficient to implement the 3 subsystems of the DDC software,The DDC project adopted the Online Software Process,which recommends a basic software life-cycle:problem statement,analysis,design,implementation and testing.Each phase results in a corresponding document or in the case of the implementation and testing,a piece of code,Inspection and review take a major role in the Online software process,The DDC documents have been inspected to detect flaws and resulted in a improved quality.A first prototype of the DDC is ready and foreseen to be used at the test-beam during summer 2001.