# Adding Data Instance Size

In the Fieldbus Settings, the user can set Data instance size, which is a general value used for size span calculations. An instance defines where should the first byte of the acyclic data be read.

This is possible only for the following Fieldbus types:

- EtherNet IP

- DeviceNet

- Profinet IO

- Profibus

- CC Link IE

1. Select a controller in the Plant structure .

2. Go to Fieldbus and SoftPLC tab.

3. Select the Overview sub-tab.

4. Enter the value in the Data instance size field.

The value for Data instance size defines how big an instance should be. This is general for all instances in the acyclic fieldbus mapping with virtual stations. Default: 64, Maximum: 255 (256 bytes).

The size span calculation for CC link is done automatically.

In this Section

- Deleting an Acyclic Fieldbus Mapping