Development of the Global Pattern Format for the LTI.

The High-Luminosity LHC (HL-LHC) will increase ATLAS trigger and data-acquisition rates to 1 MHz, requiring an updated Local Trigger Interface (LTI) for distributing TTC signals and BUSY feedback. This report presents a Global Pattern Format and associated parser that simplify the creation of LTI patterns while preserving full flexibility. The format integrates TTC, GLOBAL,
SYNCUSER, and UPSTREAM controls into a row-based table with explicit timing, trigger, and feedback fields, along with multiplicity operators and automatic gap handling. The parser is validated against firmware specifications and by reproducing a complex Liquid Argon calorimeter test sequence. To support realistic studies, two legacy ALTI pattern generators were adapted: a Python tool for simple dead-time models and a C++ tool implementing the Run-4 sliding-window scheme. Tests show accurate reproduction of expected dead-time behaviour, confirming the framework’s suitability for Phase-II LTI development and future inclusion within the low-level menu.