From 6520ac7e1cfd09d6c16d0cf47043d29be6027c8e Mon Sep 17 00:00:00 2001
From: Josef Zweck <josef@zweck.dev>
Date: Sat, 4 Jul 2026 10:31:49 +0000
Subject: [PATCH] Document modbus broadcast

---
 src/content/docs/components/modbus_server.mdx | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/content/docs/components/modbus_server.mdx b/src/content/docs/components/modbus_server.mdx
index be33b0e91de..e9ddfa8b287 100644
--- a/src/content/docs/components/modbus_server.mdx
+++ b/src/content/docs/components/modbus_server.mdx
@@ -13,6 +13,10 @@ The `modbus_server` component creates a RS485 connection to let your ESPHome nod
 
 You must set the `role` attribute of the [Modbus](/components/modbus/) to `server`.
 
+> [!NOTE]
+> Modbus broadcast writes use address `0`. They are delivered to every registered server device on the same hub and
+> do not send a response. Only write function codes `0x06` and `0x10` are treated as broadcasts.
+
 <Image src="/images/modbus.png" width={190} height={200} layout="constrained" alt="" />
 
 ## Hardware setup