README: point to docs/protocol/ for the raw manufacturer XLSX

README.md

@@ -23,7 +23,7 @@ which response belongs to which request.
 | File | Purpose |
 |------|---------|
 | `must_pv1800_monitor.py` | The monitor script. Self-contained — embeds the pyserial-based TCP proxy it runs on the remote host, plus the full PV1800 register map. |
-| `docs/register-map.md` | The PV1800 register map, derived from `taHC81/MUST-ESPhome/PH1800 PV1800 EP1800 PV3500 EP3500 RS485 Modbus RTU communication Protocol 1.4.15.xlsx`. |
+| `docs/register-map.md` | The PV1800 register map, cross-checked against the manufacturer protocol doc. |
 | `docs/quirks.md` | Things I learned the hard way about the PV1800 firmware and the CH340 driver. Read this before debugging "why isn't it working". |
 | `tools/test_proxy.py` | A standalone copy of the TCP<->serial proxy, useful for ad-hoc debugging with `nc` or `socat`. |
 
@@ -213,6 +213,7 @@ Example snapshot (panels disconnected, inverter in ByPass mode feeding a
   register map in action.
 - `PH1800 PV1800 EP1800 PV3500 EP3500 RS485 Modbus RTU communication
   Protocol 1.4.15.xlsx` (in the same repo) — the authoritative register map
+- `docs/protocol/` — raw manufacturer protocol document (XLSX), a CSV extraction, and a Markdown rendering; the XLSX is the canonical source for register definitions
   for the inverter family. Parsed copy in `docs/register-map.md`.
 
 ## Caveats / known issues