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.