Introduction

Although the official SystemRDL spec defines numerous properties that allow you to define complex register map structures, sometimes they are not enough to accurately describe a necessary feature. Fortunately the SystemRDL spec allows the language to be extended using “User Defined Properties” (UDPs).

Current UDP Support

Note: PeakRDL-BusDecoder currently does not implement any User Defined Properties. The focus of this tool is on bus decoding and address space routing rather than field-level or register-level behavioral extensions.

If you need UDPs for field-level behaviors (such as buffering, signedness, or fixed-point representations), consider using PeakRDL-regblock, which is designed for comprehensive register block generation with extensive UDP support.

Extending with Custom UDPs

If your bus decoder design requires custom User Defined Properties, you can extend PeakRDL-BusDecoder by:

1. Define your UDP in SystemRDL

   Create a .rdl file that defines your custom properties:

   property my_custom_prop {
       component = addrmap;
       type = boolean;
   };
   

2. Implement the UDP in Python

   Create a Python UDP definition class in your project:

   from systemrdl.udp import UDPDefinition
   
   class MyCustomUDP(UDPDefinition):
       name = "my_custom_prop"
       valid_components = {"addrmap"}
       valid_type = bool
       default = False
   

3. Register the UDP with the compiler

   When using PeakRDL-BusDecoder programmatically, register your UDP:

   from systemrdl import RDLCompiler
   from peakrdl_busdecoder import BusDecoderExporter
   
   rdlc = RDLCompiler()
   rdlc.register_udp(MyCustomUDP)
   
   # Compile your RDL files
   rdlc.compile_file("my_udp_defs.rdl")
   rdlc.compile_file("my_design.rdl")
   
   root = rdlc.elaborate()
   
   # Export
   exporter = BusDecoderExporter()
   exporter.export(root, "output/")
   

4. Access UDP values in your design

   UDP values can be accessed from nodes in the SystemRDL tree and used to customize the generated bus decoder logic as needed.

For more information on creating User Defined Properties, see the SystemRDL Compiler documentation.