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# Modbus wiring

The receiver **RX MODBUS** offers triple connectivity to adapt to all industrial supervision architectures (PLCs, IoT gateways, industrial PCs).

## Communication modes

Depending on your infrastructure, you can use one of the following three interfaces:

* **Modbus TCP/IP** : Connection via the integrated RJ45 port. This mode uses the Ethernet network to carry Modbus frames.
* **Modbus RTU** (Serial): Use of RS485 or RS232 links via the pre-wired multi-pair cable.

## Pinout and Color Code (Serial Link)

The RX MODBUS comes with a pre-wired cable for serial connections. Be sure to strictly follow the color code below when connecting it to your PLC:

**RS485 Link (Preferred for long distances)**

<table><thead><tr><th width="150.4609375">Wire color</th><th width="134.734375">Signal</th><th>PLC connection</th></tr></thead><tbody><tr><td><mark style="color:orange;">Brown</mark></td><td>A (+)</td><td>RX terminal / A of the PLC</td></tr><tr><td>White</td><td>B (-)</td><td>TX terminal / B of the PLC</td></tr><tr><td><mark style="color:$success;">Green</mark></td><td>GND</td><td>PLC ground (GND)</td></tr></tbody></table>

**RS232 Link (Short distances < 15m)**

<table><thead><tr><th width="149.46484375">Wire color</th><th width="134.734375">Signal</th><th>PLC connection</th></tr></thead><tbody><tr><td><mark style="color:blue;">Blue</mark></td><td>RX</td><td>TX terminal / B of the PLC</td></tr><tr><td><mark style="color:yellow;">Yellow</mark></td><td>TX</td><td>RX terminal / A of the PLC</td></tr><tr><td><mark style="color:$success;">Green</mark></td><td>GND</td><td>PLC ground (GND)</td></tr></tbody></table>

{% hint style="info" %}
The Green wire (GND) is **common** to both serial protocols. Make sure the physical mode (RS485 or RS232) selected in the RX CONFIG > General tab matches your physical wiring.
{% endhint %}

## :warning: Recommendations

To ensure effective communication between your PLC and the RX MODBUS, we recommend following the recommendations below:

{% hint style="danger" %}
**Delay** : We recommend maintaining a delay of**at least two seconds** between two consecutive Modbus requests sent to the receiver. As a reminder, the **minimum period** with which the **Enless transmitters** can be configured is **one minute**. It is therefore not necessary to configure very high polling frequencies.
{% endhint %}

{% hint style="danger" %}
**Block reading** : To optimize the polling process, we recommend reading consecutive Modbus points in blocks. This makes it possible to **reduce the number of requests** Modbus sent to the receiver. When you read Modbus points in blocks, we recommend **not exceeding 64 points at a time**.
{% endhint %}

{% hint style="danger" %}
**Number of clients:** The Enless receiver acts as a server and can only accept**one TCP client at a time**. Being queried by another Modbus device may disrupt Modbus communication with the connected TCP client.
{% endhint %}


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