49Implementation

Set an imported RTL parameter

The elaboration defect

mkInitializedRegister constructs external RTL whose initial contents come from a Verilog parameter. The frozen BVI declaration already maps its BSV constructor argument to that parameter, but the editable constant supplies the wrong argument. The starter therefore builds valid hardware with the wrong initial state; this is not a runtime write failure.

Only the declaration of importedInitialValue is editable. Preserve its type, the wrapper, BVI declaration, and mkTop.

Read and predict before editing

Follow the static path first:

importedInitialValue -> mkInitializedRegister -> mkImportedReg argument -> RTL init parameter.

Then follow the runtime observation: mkTop.show calls imported.read before performing any write. Before Run, predict whether the starter will compile and which source declaration determines the displayed initial value. Distinguish the constructor choice made while hardware is elaborated from read, which only observes the resulting instance at runtime.

Minimal repair and completion

Set the editable 8-bit constant to represent the required hexadecimal initial state, 2a. Do not alter the BVI parameter assignment or add an initialization rule.

After Run, the first read must show the requested initial state without any preceding write call. A correct repair explains both phases: changing the constant selects a differently parameterized RTL instance at build time, while the method protocol and runtime wiring stay unchanged.

Progressive hints

Transfer experiment

After completing the task, choose a different 8-bit initial pattern and predict the first read. This experiment requires rebuilding the design: a parameter is fixed per generated instance and cannot be changed by a later method call.