One Size Fits All: Multiple Uses of Common Modules in the ATLAS Level-1 Calorimeter Trigger

The architecture of the ATLAS Level-1 Calorimeter Trigger has been improved and simplified by using a common module to perform different functions that originally required three separate modules.The key is the use of FPGAs with multiple configurations, and the adoption by different subsystems of a common high-density custom crate backplane that takes care to make data paths equal widths and includes minimal VMEbus.One module design can now be configured to count electron/photon and tau/hadron clusters, or count jets, or form missing and total transverse-energy sums and compare them to thresholds.In addition, operations are carried out at both crate and system levels by the same module design.