# Node Editor

The **Data Flow** tab hosts a Blender-inspired block-diagram canvas
where pccx-v002 topology nodes can be dragged, wired, and tweaked
interactively.

```{image} /_static/screenshots/node-editor.png
:alt: pccx-lab Node Editor with the default NPU dataflow and minimap
:width: 100%
```

## Layout

| Area | Role |
|------|------|
| **Left palette** | Categorised, collapsible, searchable node library (Input / Memory / Compute / Output) |
| **Canvas**       | Infinite pan/zoom, minimap overlay, zoom controls |
| **Quick-add**    | `Shift+A` floating popover anchored at the cursor — same convention as Blender |

## Node catalogue

Thirteen node types ship in the default build; five are pccx-v002
specific and mirror the actual KV260 accelerator topology.

### Input

- **Host CPU** — AXI-Lite master, configurable PCIe / CXL interface.

### Memory

- **DRAM** — off-chip: LPDDR5 / HBM2E / DDR5 / GDDR6X with tunable BW + capacity
- **AXI Fabric** — 128-bit interconnect with burst length, overhead, and port count
- **BRAM L1** — on-chip scratchpad, per-port BW and bank count
- **URAM L2** (v002) — 64 URAMs, 1.75 MB, 2-cycle read
- **HP Buffer** (v002) — 4-port HP AXI pre-fetch FIFO, separate upper / lower weight channels
- **fmap Cache** (v002) — 27 b × 2048 entries, 32-lane broadcast

### Compute

- **GEMM MAC Array** (v002) — 32 × 32 W4A8 systolic, 65.5 TOPS at 1 GHz
- **GEMV Engine** (v002) — 4 lanes × 32 MAC, 5-stage pipeline
- **CVO SFU** (v002) — single instance, CORDIC + LUT for exp / sqrt / GELU / sin / cos / softmax
- **Accumulator** — register file + adder tree

### Output

- **Post-Proc** — activation / normaliser / quantiser / softmax toggle
- **Write-back DMA** — 1 / 2 / 4 / 8-channel egress

## Keyboard shortcuts

| Shortcut | Action |
|----------|--------|
| `Shift+A`           | Open quick-add menu at cursor |
| `Esc`               | Close quick-add menu |
| `Delete` / `Backspace` | Remove selected node(s) / edge(s) |
| Scroll              | Zoom in / out |
| Drag canvas         | Pan |
| Drag palette entry  | Spawn at drop position |
| Double-click entry  | Spawn at canvas centre |

Ctrl-Scroll / pinch-zoom also work. The palette collapse state is
per-category, not per-session — refresh keeps it expanded.

## Typed sockets (colour legend)

Each node exposes one or more coloured handles:

| Colour | Data type |
|--------|-----------|
| `#94a3b8` grey       | command / control |
| `#60a5fa` blue       | AXI read / stream |
| `#818cf8` indigo     | AXI fabric / interconnect |
| `#22d3ee` cyan       | fmap / broadcast channel |
| `#34d399` green      | tile A / primary compute stream |
| `#a78bfa` violet     | tile B / MAC partial sum |
| `#f59e0b` amber      | accumulator / stall |
| `#fb923c` orange     | post-proc output |
| `#f472b6` pink       | DMA egress / write-back |
| `#e879f9` fuchsia    | SFU / non-linear |
| `#f87171` red        | HP buffer input |
| `#14b8a6` teal       | URAM read / L2 |
| `#eab308` yellow     | fmap cache broadcast |

The default wiring mirrors the pccx v002 dataflow (Host → AXI → BRAM →
MAC → Accumulator → Post-Proc → Write-back), so the canvas is already a
valid starting point for experimentation.

## Roadmap

- Frame / group (nested sub-graphs, Blender style).
- Typed socket validation — reject mismatched drops with a visible tooltip.
- SVG / PNG export of the current canvas.
- Animated data-flow playback synced to the loaded `.pccx`.