---
title: Make a Link’nX scenario conditional on a KNX group address value
description: "Start a Link’nX scenario only if a KNX group address is True or False, or crosses a threshold: address, DPT, operator and value to enter in the condition."
canonical: https://wiki.can-nx.com/en/guides/link-condition-knx/
language: en
product: Link’nX
audience:
  - administrateur
  - installateur
context: "Link’nX web: KNX condition, selected in the scenario’s KNX condition field"
---

# Make a Link’nX scenario conditional on a KNX group address value

Context: Link’nX web: KNX condition, selected in the scenario’s KNX condition field

The **KNX** condition in Link’nX compares the value received on a group address with a criterion: equality for a Boolean DPT, comparison with a threshold for a numeric DPT. The scenario starts only if this criterion is met. The condition reads a value; creating it does not force any new value into the equipment.

Intended for installers and administrators. To start a scenario when a KNX write is received, prepare a [KNX trigger](https://wiki.can-nx.com/en/guides/link-trigger-knx/) instead: the condition, for its part, allows or blocks the start requested by a trigger.

## Before you start

- You know the full group address, its DPT and the expected value.
- If not, ask the installer or support for this information. Do not choose an object only because its name resembles that of the equipment.

## Enter the group address and the DPT

1. In **Conditions**, click **Add**, then choose **KNX** in **Select a condition type**.
2. Fill in **Name**, which is required and limited to 64 characters.
3. In **Group Address**, enter the full known address. The format consists of three numbers separated by slashes: first number from 0 to 31, second from 0 to 7, third from 0 to 255. **1/1/1** is a fictitious format example, not an address to reuse without checking.
4. Fill in **DPT** with the data type of this address. You can search for its number in the DPT suggestions, then select it. The expected format has a non-zero main part of one to three digits and a sub-part of three or four digits after the dot.

The address list may suggest the available ETS objects. For this procedure, manually entering the full known address lets you control precisely which address is used. The form only checks the DPT format: check in the KNX project that it matches the equipment’s object.

## Define the comparison criterion

| DPT entered | Fields to fill in | Criterion |
| --- | --- | --- |
| Starts with **1.** | **Value**: **True** or **False** | Equality with the received value |
| Other numeric DPT | **Operator**: **Equal to ( = )**, **Greater than ( > )** or **Lower than ( < )**, then **Value** | Comparison of the value received from the address with this threshold |

**Operator** is initially set to **Equal to ( = )**: change it to compare with a threshold. A value of 0 can be entered; a negative value is appropriate only if the DPT and the need allow it.

## Save and add the condition to the scenario

1. Click the floppy disk icon, then follow the [save confirmations](https://wiki.can-nx.com/en/guides/link-condition-edit/).
2. In the scenario, open **KNX condition**, select this condition, then save the scenario. When several KNX conditions are selected, all of them must be met.

## Check the result

- Reopen the condition and check the saved address, DPT, operator and value.
- To test, watch the value actually sent on the group address, for example with the ETS group monitor. The state visible on the equipment is not enough: the condition depends on the KNX value received.

## Troubleshooting

| Message | Action |
| --- | --- |
| **Issue with field 'Group Address'. Incorrect format** | Check the three numbers and the slashes |
| **Issue with field 'DPT'. Incorrect format.** | Check the number and the dot |
| **Issue with field 'Value'. It requires a value.** | Choose **True** or **False**, or enter the numeric threshold according to the DPT |

If the scenario does not start while you expect a condition to be met, check the saved address, DPT, comparison direction and threshold. Then check the condition selection, the other conditions and the activation of the scenario. For a text comparison or a data type not covered by this numeric entry, also contact support.

If the problem persists, contact support@can-nx.com with the expected criterion, the time and the checks already made, without repeating write commands.