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For transmitting BOOL data, it's possible to use one bit from a 16-bit word register. As for INT data (integer numbers), they can also be transmitted via Modbus TCP by placing them in two consecutive 16-bit word registers.

The Modbus registers of a device are organized around the four basic data reference types noted above and this data type is further identified by the leading number of the reference address as follows: 

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Sorce:

https://help.codesys.com/api-content/2/codesys/3.5.13.0/en/_cds_f_networkvariables/
https://forge.codesys.com/forum/en/124/genmed-Network_Functionality_V23.pdf

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