# 讀寫型記憶體讀取指令(03)

{% hint style="info" %}
讀取指令中register長度必需小於等於 20個 register。超過該長度的指令會被忽略。
{% endhint %}

## 指令範例

### 控制端發指令(03)格式

| Byte#      | 1             | 2             | 3         | 4         | 5              | 6              | 7   | 8   |
| ---------- | ------------- | ------------- | --------- | --------- | -------------- | -------------- | --- | --- |
| Node ID    | Slave Address | Function Code | 讀取數據的啟始地址 | 讀取數據的啟始地址 | 讀取registers 總數 | 讀取registers 總數 | CRC | CRC |
| 範例內容01\~FF | 01            | 03            | 00        | 00        | 00             | 03             | 05  | CB  |

#### 控制端發訊範例說明

這個範例會讀取A01的管徑選項及A02 Scale Factor

slave address: 01(本流量計地址)

function code: 03(讀取指令)

讀取數據的啟始地址: 0000(要讀取的數據的啟始地址)

讀取registers 總數: 0003 (需要從 0000 開始讀三個 register 的記憶體)

CRC: 05 CB (依 CRC 算法計算出的糾錯碼)

### 流量計回覆(03)格式

| Byte#      | 1             | 2             | 3        | 4            | 5                         | 6                         | 7                         | 8                      | 9                         | 10  | 11  |
| ---------- | ------------- | ------------- | -------- | ------------ | ------------------------- | ------------------------- | ------------------------- | ---------------------- | ------------------------- | --- | --- |
| Node ID    | Slave Address | Function Code | 回覆的Byte數 | Data Byte #1 | <p>Data Byte</p><p>#2</p> | <p>Data Byte</p><p>#3</p> | <p>Data Byte</p><p>#4</p> | <p>Data Byte<br>#5</p> | <p>Data Byte</p><p>#6</p> | CRC | CRC |
| 範例內容01\~FF | 01            | 03            | 06       | 00           | 00                        | 3F                        | 80                        | 00                     | 00                        | 2C  | 89  |

#### 流量計回覆範例說明

slave address: 01(本流量計地址)

function code: 03(讀取指令)

回覆的Byte數: 06(3個register=6byte)

Data Byte:&#x20;

* 00 00(目前管徑是1inch PVC)&#x20;
* 3F 80 00 00(目前的Scale Factor 是 1.0)

CRC: 2C 89 (依 CRC 算法計算出的糾錯碼)


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