Examples

Two designs ship with the repository: a small streaming accelerator used by the tests and the docs, and a five-stage processor from the parser test suite.

Demo: streaming accelerator

Source: packages/web/samples/demo/demo.sv. A top with an input FIFO, a controller, a compute block (two instances of a processing-element module, an accumulator, a mux, an adder) and an output FIFO. It has buses, fanout (clock and reset), feedback (ready/valid back-pressure and the accumulator loop), constants and a struct-free, parser-friendly style.

Open it: automatic layout · with layout rules · with the conflicting rule file

Demo top level with layout rules — Top level with `demo.layout.yaml`: datapath on one row with fixed gaps, controller above compute, a 640×420 frame for compute.

compute expanded in place with the fifo_data net highlighted — `compute` expanded in place; the `fifo_data` net is selected and the highlight continues into `data_in` inside the frame.

compute focused as the main schematic — *Focus module* on `compute`: the two PEs, the adder and mux, the `always_ff` register block, and feedback lanes below.

controller focused — The controller: comparators, gates, an `always_comb` next-state block and an `always_ff` state register, with the 2-bit `state` bus drawn thicker.

ProcBase: a five-stage TinyRV2 processor

Source: core/tests/examples/ProcBase.v and its dependencies, from a course processor lab. ProcBase.v carries the // verilens: top pragma, and ProcBase.layout.yaml next to it puts the control unit before and above the datapath, gives both a readable frame, orders the datapath ports, and pins the pipeline stage order inside dpath.

cd core/tests/examples
../../../verilens ProcBase.v ProcBaseDpath.v ProcBaseCtrl.v DropUnit.v ProcDpathAlu.v ProcDpathImmGen.v \
  IntMulAlt.v Lookahead.v muxes.v arithmetic.v regfiles.v tinyrv2_encoding.v -l ProcBase.layout.yaml

Twelve files, 22 modules. Six vc_* library cells (queues, enable registers, trace modules) are not part of the examples and render as dashed black boxes. Open the generated page ↗

ProcBase top level — Top level: `ctrl` above and left of `dpath`, queues and the instruction drop unit around them, black boxes dashed.

ProcBase with dpath expanded — `dpath` expanded in its 960×560 frame: fetch, decode, execute, memory and writeback left to right; the surrounding boxes have not moved.

Things worth clicking: the inst_D bus from the datapath back to the controller (a feedback route), the multiplier instance three levels deep (dpath → multiplier → …), and the diagnostics drawer, which reports two multiply-driven nets caused by struct-field assigns in the original source.

Writing your own layout file

Start from automatic layout, open the Layout tab, and add rules one at a time. Required rules are for things that must hold (stage order, a block that must sit left of another); preferred rules are for taste (rows, something above something else). The DSL page has the full semantics and the demo rule file; core/tests/examples/ProcBase.layout.yaml is the larger example.