Newad: A register map automation tool for Verilog

Vamsi Vytla and Larry Doolittle

Abstract

Large scale scientific instrumentation-and-control FPGA gateware designs have numerous run-time settable parameters. These can be used either for user-level control or by automated processes (e.g., calibration). The number of such parameters in a single design can reach on the order of 1000, and keeps evolving as the gateware and its functionality evolves. One must keep track of which module the registers belong to, where the registers need to be decoded, and how to express the properties (or even semantics) of the register to the next level of user or software. Note, the registers maybe embedded anywhere throughout the module hierarchy. Purely manual handling of these tasks by HDL developers is considered burdensome and error-prone at this scale. Typically these registers are writable via an on-chip bus, vaguely VME-like, that is controlled by an on-chip or off-chip CPU. There have been several attempts in the community to address this task at different levels. However, we have found no tool that is able to generate a register map, generate decoders and encoders with minimal overhead to the developer. So, here we present a tool that scours native HDL source files and looks for specific language-supported attributes and automatically generates a register map and bus decoders, respecting multiple clock domains, and presents a JSON file to the network that maps register names to addresses.