The Seamax 463E unit used to work with the Seamax library, but now it uses the C# NModbus library for control. In the test bench, there is a set of relays that are turned on and off by the Sealevel 463E master, which is set up with Modbus. The first three registers of the Sealevel 463E are for managing the device, and the last six can be connected to other devices.

https://www.sealevel.com/seai-o-463e/
https://www.sealevelsoftware.com/documentation/seamax/win/_enumerations.html
https://www.sealevelsoftware.com/documentation/seamax/win/sea_i_o46x_registers.html
https://www.sealevelsoftware.com/documentation/seamax/win/mbbd_seaio_463.html
https://files.icp-deutschland.de/produkte/KC004079/web/SeaIO-Modules-User-Manual-4.pdf
https://github.com/NModbus/NModbus
https://github.com/NModbus4/NModbus4