retroSoC/docs/mini-soc-block-diagram.dot

// Mini SoC architecture overview.
// Render with: dot -Tsvg docs/mini-soc-block-diagram.dot -o docs/mini-soc-block-diagram.svg
// Sources of truth: rtl/mini/top/{retrosoc_asic,retrosoc,bus}.sv and
// rtl/mini/integration/{soc_topology,user_extensions,clock_reset_domains}.json.
digraph mini_soc_block_diagram {
  graph [
    bgcolor="transparent",
    compound=true,
    fontname="Arial",
    fontsize=18,
    label="retroSoC Mini SoC Architecture",
    labelloc="t",
    labeljust="l",
    newrank=true,
    nodesep=0.38,
    rankdir=TB,
    ranksep=0.62,
    splines=polyline
  ];

  node [
    color="#4B5563",
    fontcolor="#111827",
    fontname="Arial",
    fontsize=10,
    margin="0.12,0.08",
    penwidth=1.1,
    shape=box,
    style="rounded,filled"
  ];
  edge [
    arrowsize=0.7,
    color="#4B5563",
    fontcolor="#374151",
    fontname="Arial",
    fontsize=8,
    penwidth=1.2
  ];

  ext_clock [
    fillcolor="#F3F4F6",
    label="External clocks and reset\next_clk, aud_clk, reset"
  ];
  ext_io [
    fillcolor="#F3F4F6",
    label="External I/O and memory\nGPIO, UART0, XPI Flash, SDRAM, PSRAM\nSD card, I2C, I2S, DVP and serial I/O"
  ];

  subgraph cluster_asic {
    color="#111827";
    fontcolor="#111827";
    fontname="Arial";
    fontsize=14;
    label="retrosoc_asic";
    margin=18;
    style="rounded";

    rcu [
      fillcolor="#EDE9FE",
      label="RCU\nclock buffering and reset synchronization\nPLL request/acknowledgment CDC"
    ];

    subgraph cluster_soc {
      color="#94A3B8";
      fontcolor="#334155";
      fontname="Arial";
      fontsize=12;
      label="retrosoc";
      margin=16;
      style="rounded,dashed";

      mgmt_core [
        fillcolor="#DDF2E3",
        label="Management core\nHazard3 by default\nPicoRV32 build option"
      ];
      mgmt_adapter [
        fillcolor="#E5E7EB",
        label="RIBP2RIB"
      ];
      user_core [
        fillcolor="#DDF2E3",
        label="Selected user core\nC0-C4, one active"
      ];
      dma [
        fillcolor="#DDF2E3",
        label="DMA\nRIB master and RIBP target"
      ];
      fabric [
        fillcolor="#DCECF8",
        label="RIB fabric\n3-master round-robin arbitration\nINCR1 / INCR4, access policy, fault reporting",
        shape=hexagon
      ];
      fault [
        fillcolor="#FCE7F3",
        label="Error slave\naccess and protocol faults"
      ];
      sram [
        fillcolor="#FFF3C9",
        label="On-chip SRAM\noptional RIB2RAM path"
      ];
      ribp_adapter [
        fillcolor="#E5E7EB",
        label="RIB2RIBP"
      ];
      apb_adapter [
        fillcolor="#E5E7EB",
        label="RIB2APB\ndirect APB bridge"
      ];
      sysctrl [
        fillcolor="#F9E1E7",
        label="SYSCTRL and CLINT\nPLL, user-core select/reset/bus enable\nfault and performance control"
      ];
      ribp_targets [
        fillcolor="#F9E1E7",
        label="RIBP target wrapper\nXPI/Flash, SDRAM, PSRAM, SPI-SD, DVP\nGPIO, UART0, timers, I2C, I2S and 1-Wire"
      ];
      apb_targets [
        fillcolor="#E6F4EA",
        label="APB target wrapper\nArchinfo, RNG, UART1, PWM, PS/2, RTC\nwatchdog, CRC, advanced timer and user IP"
      ];
      gpio_bridge [
        fillcolor="#E5E7EB",
        label="GPIO pad bridge\nsoftware, alternate and user modes"
      ];
      irq [
        fillcolor="#FCE7F3",
        label="Interrupt aggregation\nRIBP and APB target IRQs to management core"
      ];
    }
  }

  { rank=same; mgmt_core; user_core; dma; }
  { rank=same; fault; fabric; sram; }
  { rank=same; ribp_adapter; apb_adapter; }
  { rank=same; sysctrl; ribp_targets; apb_targets; }
  { rank=same; gpio_bridge; irq; }

  ext_clock -> rcu [label="clock / reset"];
  rcu -> fabric [label="system clock / reset", style=dashed];

  mgmt_core -> mgmt_adapter [label="RIBP"];
  mgmt_adapter -> fabric [label="RIB"];
  user_core -> fabric [label="RIB"];
  dma -> fabric [label="RIB"];

  fabric -> fault [label="invalid / denied", dir=both];
  fabric -> sram [label="RIB"];
  fabric -> ribp_adapter [label="RIB"];
  fabric -> apb_adapter [label="RIB"];
  ribp_adapter -> sysctrl [label="RIBP"];
  ribp_adapter -> ribp_targets [label="RIBP"];
  apb_adapter -> apb_targets [label="APB"];

  ribp_targets -> gpio_bridge [label="GPIO alternate functions"];
  apb_targets -> gpio_bridge [label="user_gpio"];
  ribp_targets -> ext_io [dir=both, label="device interfaces"];
  gpio_bridge -> ext_io [dir=both, label="pad control"];
}