This property - together with the start address - is used to determine the address range of the PLC card. The data length indicates the number of bits up to the next free address on the next PLC card. PLC devices exist that consist of several integrated modules, meaning subdevices, and that have several start addresses. Such a device can consist, for example, of an internal CPU module, an internal input-output module as well as internal counter module - however with only one part number. In order to map such logical function units within a PLC device, up to twelve PLC subdevices are available to you. Enter the number of bits for the inputs of the PLC subdevice, for example "8", here. Note that there are PLC cards, for example technology modules, which are only assigned to a few inputs / outputs, but still require a larger address range. Always enter the maximum required size for the address range of the inputs here.

Reference

MDPartsDatabaseItemPropertyList Class
MDPartsDatabaseItemPropertyList Members