freechips/semicustom/semicustom-inverter.ipynb

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   "source": [
    "# Semicustom digital design demo using OpenROAD"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Sources"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "id": "uINjDJNf39eD"
   },
   "source": [
    "### RTL description (Verilog)\n",
    "\n",
    "The OpenROAD workflow takes the circuit's RTL description as an input. For instance, it can be a three bits XOR gate."
   ]
  },
  {
   "cell_type": "code",
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   "source": [
    "%%writefile v/inverter.v\n",
    "module inverter(\n",
    "    input wire a,\n",
    "    input wire b,\n",
    "    input wire c,\n",
    "    output wire out\n",
    ");\n",
    "    assign out = a ^ b ^ c;\n",
    "endmodule"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "id": "hp8h5vH8TUXr"
   },
   "source": [
    "### Configuration file (JSON)\n",
    "\n",
    "A configuration file should be provided. It describes constraints and strategies applied during synthesis and implementation of the circuit."
   ]
  },
  {
   "cell_type": "code",
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   "source": [
    "%%writefile config.json\n",
    "{\n",
    "    \"DESIGN_NAME\": \"inverter\",\n",
    "    \"VERILOG_FILES\": \"dir::v/inverter.v\",\n",
    "    \"CLOCK_TREE_SYNTH\": false,\n",
    "    \"CLOCK_PORT\": null,\n",
    "    \"PL_RANDOM_GLB_PLACEMENT\": true,\n",
    "    \"FP_SIZING\": \"absolute\",\n",
    "    \"DIE_AREA\": \"0 0 40 40\",\n",
    "    \"PL_TARGET_DENSITY\": 0.8,\n",
    "    \"FP_PDN_AUTO_ADJUST\": false,\n",
    "    \"FP_PDN_VPITCH\": 10,\n",
    "    \"FP_PDN_HPITCH\": 10,\n",
    "    \"FP_PDN_VOFFSET\": 5,\n",
    "    \"FP_PDN_HOFFSET\": 5,\n",
    "    \"DIODE_INSERTION_STRATEGY\": 3\n",
    "}"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Workflow\n",
    "The provided `flow.tcl` is a script describing the OpenROAD workflow. A _GDS_ file will be generated using the RTL circuit description, the PDK and the configuration file."
   ]
  },
  {
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    "id": "VP60fdObiP15",
    "outputId": "41aa85e4-c663-4778-d448-928dbe474b11"
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   "outputs": [],
   "source": [
    "%env PDK=sky130A\n",
    "!flow.tcl -design ."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Output products"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "id": "luguFgZ43AeL"
   },
   "source": [
    "### Display layout\n",
    "\n",
    "The implemented layout can be retrieved as follows:"
   ]
  },
  {
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   "source": [
    "import glob\n",
    "import gdstk\n",
    "import IPython.display\n",
    "\n",
    "gdsii = sorted(glob.glob(\"./runs/*/results/final/gds/*.gds\"))[-1]\n",
    "top = gdstk.read_gds(gdsii).top_level()\n",
    "top[0].write_svg('svg/inverter.svg')\n",
    "IPython.display.SVG('svg/inverter.svg')"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "id": "NW_7YdgTZYQK"
   },
   "source": [
    "### Reporting\n",
    "\n",
    "Many reports are available under:\n",
    "\n",
    "```\n",
    "freeechips/semicustom/runs/RUN_YYYY.MM.DD_HH.MM.SS/reports/.\n",
    "```\n",
    "\n",
    "An overview of the main figures can be retrieved as well:"
   ]
  },
  {
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   "execution_count": null,
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    "outputId": "d50dcf9f-30cd-42a3-dab5-12992bc9dca2",
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   },
   "outputs": [],
   "source": [
    "import glob\n",
    "import pandas as pd\n",
    "\n",
    "metrics = pd.read_csv(sorted(glob.glob(\"./runs/*/reports/metrics.csv\"))[-1])\n",
    "\n",
    "print(f\"tritonRoute_violations  {metrics['tritonRoute_violations'][0]}\")\n",
    "print(f\"Short_violations        {metrics['Short_violations'][0]}\")\n",
    "print(f\"OffGrid_violations      {metrics['OffGrid_violations'][0]}\")\n",
    "print(f\"MinHole_violations      {metrics['MinHole_violations'][0]}\")\n",
    "print(f\"Other_violations        {metrics['Other_violations'][0]}\")\n",
    "print(f\"Magic_violations        {metrics['Magic_violations'][0]}\")\n",
    "print(f\"pin_antenna_violations  {metrics['pin_antenna_violations'][0]}\")\n",
    "print(f\"net_antenna_violations  {metrics['net_antenna_violations'][0]}\")\n",
    "print(f\"lvs_total_errors        {metrics['lvs_total_errors'][0]}\")\n",
    "print(f\"cvc_total_errors        {metrics['cvc_total_errors'][0]}\")\n",
    "print(f\"klayout_violations      {metrics['klayout_violations'][0]}\")"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# To have fun going further...\n",
    "\n",
    "## High-Level Synthesis (HLS)\n",
    "\n",
    "RTL description of circuits does not follow an imperative programming paradigm. It is a description language that produces highly parallelized designs.\n",
    "\n",
    "High-Level Synthesis provides an imperative language and a compiler that synthesizes the imperative instructions into RTL. For instance, _XLS_ provides a _Rust_-like language:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "%%writefile xls/x/adder.x\n",
    "pub fn adder(in1: u1, in2: u1) -> u2 {\n",
    "  let sum: u2 = in1 as u2 + in2 as u2;\n",
    "  sum\n",
    "}\n",
    "\n",
    "#[test]\n",
    "fn adder_test() {\n",
    "  let _= assert_eq(adder(u1:0, u1:0), u2:0b00);\n",
    "  let _= assert_eq(adder(u1:0, u1:1), u2:0b01);\n",
    "  let _= assert_eq(adder(u1:1, u1:1), u2:0b10);\n",
    "  _\n",
    "}"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Testing, parsing and linting can be performed prior to RTL synhesis:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "scrolled": true
   },
   "outputs": [],
   "source": [
    "!interpreter_main xls/x/adder.x"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Now that the imperative instructions are tested, the RTL design ca nby synthesized by _XLS_:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "XLS_DESIGN_NAME = 'adder'\n",
    "!ir_converter_main --top={XLS_DESIGN_NAME} xls/x/{XLS_DESIGN_NAME}.x > xls/ir/{XLS_DESIGN_NAME}.ir\n",
    "!opt_main xls/ir/{XLS_DESIGN_NAME}.ir > xls/ir/{XLS_DESIGN_NAME}_opt.ir\n",
    "!codegen_main --generator=combinational xls/ir/{XLS_DESIGN_NAME}_opt.ir > v/{XLS_DESIGN_NAME}.v\n",
    "!cat v/{XLS_DESIGN_NAME}.v"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# References\n",
    "Inspired from:\n",
    "“Silicon Notebooks.” CHIPS Alliance, Apr. 08, 2023. Accessed: Apr. 10, 2023. [Online]. Available: https://github.com/chipsalliance/silicon-notebooks/blob/b65134a43b01ae31423f7ee87110740b2257ac42/digital-inverter-openlane.ipynb (Apache License 2.0)"
   ]
  }
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