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cxxrtl: provide a way to perform unobtrusive power-on reset.

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Although it is always possible to destroy and recreate the design to
simulate a power-on reset, this has two drawbacks:
  * Black boxes are also destroyed and recreated, which causes them
    to reacquire their resources, which might be costly and/or erase
    important state.
  * Pointers into the design are invalidated and have to be acquired
    again, which is costly and might be very inconvenient if they are
    captured elsewhere (especially through the C API).
This commit is contained in:
whitequark 2020-12-02 08:25:27 +00:00
parent 7b0cfd5c36
commit 5beab5bc17
4 changed files with 78 additions and 3 deletions
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8
backends/cxxrtl/cxxrtl_capi.h
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@ -55,6 +55,14 @@ cxxrtl_handle cxxrtl_create(cxxrtl_toplevel design);
// Release all resources used by a design and its handle.
void cxxrtl_destroy(cxxrtl_handle handle);
// Reinitialize the design, replacing the internal state with the reset values while preserving
// black boxes.
//
// This operation is essentially equivalent to a power-on reset. Values, wires, and memories are
// returned to their reset state while preserving the state of black boxes and keeping all of
// the interior pointers obtained with e.g. `cxxrtl_get` valid.
void cxxrtl_reset(cxxrtl_handle handle);
// Evaluate the design, propagating changes on inputs to the `next` value of internal state and
// output wires.
//