# Using the Modbus Plugin

Once the Modbus plugin has been installed and loaded into a project, you can configure Cognex Designer to be a Modbus Client, a Modbus Server, or both. Modbus communication can be implemented in Cognex Designer by using the following available Modbus-specific Devices, Task Blocks or Tag associations:

## Modbus Devices

If the Modbus plugin is loaded into the project, an additional Modbus communications node appears in the Devices > Communications category of the Project Explorer. Right-click on the Modbus node to set up a new Modbus Client Device or Modbus Server Device.

Once a Modbus Client and/or Server Device is set up in the Project Explorer, you can use their published API to perform Modbus read/write operations while the project is deployed or is in Test Mode.

## Modbus Blocks

If the Modbus plugin is loaded into the project, two Modbus-specific blocks will become available in the Toolbox for the Task Editor under the Communication > Modbus node: Read Data and Write Data. These blocks allow you to perform Modbus client read and write operations within a Task.

## Tag Assocations

The Modbus plugin also supports implementing Modbus server-client communications using Cognex Designer Tag Associations:

- In the case of Modbus Server Devices, you can use the Modbus Server Configuration UI to assign Tags to specific memory addresses of the Modbus Server device. This allows you to expose some portions of the local Modbus Server storage as tags. See the Modbus Server Device – Assigning Tag Associations to Modbus Storage topic for more information.
- In the case of Modbus Client Devices, you can use the Cognex Designer Tag Selected Path functionality to implement read/write operations.

Note: The Modbus Protocol does not define whether the addressing of the coils and registers are 0-based or 1-based. 0-based addressing is used in the Modbus Plugin.