DSP Online Algorithms for the ATLAS TileCal Read-Out Drivers

TileCal is the hadronic tile calorimeter of the ATLAS experiment at LHC/CERN. The central element of the back-end system of the TileCal detector is the read-out driver (ROD).The main components of the TileCal ROD are the digital signal processors (DSPs) placed on the processing unit (PU) daughterboards. This paper presents a detailed description of the code developed for the DSPs. The code is divided into two different parts: the first part contains the core functionalities and the second part the reconstruction algorithms. The core acts as an operating system and controls configuration, data reception and transmission and synchronization between front-end data and the timing, trigger and control (TTC) information. The reconstruction algorithms implemented on the DSP are the optimal filtering (OF), muon tagging (MTag) and missing E_T calculation. The OF algorithm reconstructs the deposited energy and the arrival time of the signal for every calorimeter channel within a front-end module. This reconstructed energy is used by the MTag algorithm to tag low transverse momentum muons that may escape the ATLAS muon spectrometer level 1 trigger whereas the missing E_T algorithm computes the total transverse energy and the projection on X and Y axis for the entire module that will be used by the level 2 trigger system.