digraph debug_arch {
  rankdir=LR;
  node [shape=box, style=rounded];

  subgraph cluster_debugger {
    label="External Debugger";
    debugger [shape=none, label=""];
  }

  subgraph cluster_debug_module {
    label="Debug Module";
    debug_module [shape=none, label=""];
  }

  subgraph cluster_core {
    label="Kelvin Core";
    core [shape=none, label=""];
  }

  debugger -> debug_module [label="ext.req / ext.rsp"];
  debug_module -> core [label="csr, scalar_rd, float_rd, haltreq, resumereq, ndmreset"];
  core -> debug_module [label="csr_rd, scalar_rs, float_rs, resumeack, halted, running, havereset"];
}