> For the complete documentation index, see [llms.txt](https://docs.lorric.com/qr/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.lorric.com/qr/fp-as510-paddle-wheel-flowmeter-manual-chinese-v2/communication/modbus-rtu-protocol.md).

# Modbus RTU Protocol

### 通訊格式 <a href="#tong-xun-ge-shi" id="tong-xun-ge-shi"></a>

| **名稱**            | **數值**          | **描述**                       |
| ----------------- | --------------- | ---------------------------- |
| 位元順序(Bit Order)   | lsb first       | 數據傳輸時，從最低有效位元 (LSB) 開始傳輸。    |
| 位元組順序(Byte Order) | big endian      | 數據傳輸時，從最高有效位元組 (MSB) 開始傳輸。   |
| 數據位(Data bits)    | 8               | 每個字元或位元組由 8 個數據位組成。          |
| 校驗位(Parity)       | None            | 傳輸過程中不使用奇偶校驗位進行錯誤檢查。         |
| 停止位(Stop bits)    | 1               | 每個字元結束後使用 1 個停止位。            |
| 浮點數標準             | IEEE 754-1985   | 浮點數（Float32）採用 32 位單精度浮點數格式。 |
| Register          | 2 Byte / 16 bit | Modbus RTU 記憶體通訊的單位長度。       |
| Byte              | 8 bit           | 數據傳輸的基本單位長度。                 |

在 Modbus RTU 通訊中，Register（暫存器）是記憶體通訊的基本單位，其長度為 **2 Byte（16 bit）**；而 Byte（位元組）則是資料傳輸的基本單位，長度為 **8 bit**。

### 記憶體定義及功能 <a href="#ji-yi-ti-ding-yi-ji-gong-neng" id="ji-yi-ti-ding-yi-ji-gong-neng"></a>

| **記憶體類型** | **唯讀型記憶體(Read-Only Memory)** | **讀寫型記憶體(Read/Write Memory)**     |
| --------- | ---------------------------- | --------------------------------- |
| 主要功能      | 讀取設備的即時狀態和結果                 | 設定設備的運行參數和校正值                     |
| 儲存內容      | 儲存流量狀態相關的記憶體，例如：瞬時流量、累計流量等   | 儲存流量設定參數相關記憶體，例如：管徑外徑、標定係數、流量截止值等 |
| 操作權限      | 只能讀取，無法寫入                    | 可供讀取和寫入                           |
| 功能碼       | 讀取指令 04                      | 讀取指令 03寫入指令 06 / 30 /31           |

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