OpenFPGA/docs/source/arch_lang/generality.rst

General Hierarchy
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The extension of the VPR architectural description language is developed as an independent branch of the original one. Most of the FPGA-SPICE descriptions are located under a XML node called <spice_settings>, which is a child node under the root node <architecture>. 
Under the <spice_settings>, a number of child node are created for describing SPICE simulation settings, technology library and transistor-level modeling of circuit modules.
In the following sub-sections, we will introduce the structures of these XML nodes and the parameters provided.