叫ModbusRTU.lib。
https://infosys.beckhoff.com/content/1033/tf6255_tc3_modbus_rtu/186519307.html?id=5842524074925149975
https://infosys.beckhoff.com/content/1033/tcplclibmodbusrtu/9007199710009867.html?id=3545230319628477492
