IEEE 754 Double-Precision Floating Point Data Type 16

By default, the interface interprets values of Data Type 16 (double-precision floating point) in a nonstandard way. Specifically, it removes the first two bytes it receives from the PLC and appends them to the end of the remaining six bytes before interpreting the eight-byte result as an IEEE 754 double-precision floating point number.

To read double-precision floating point numbers directly from eight consecutive bytes (four consecutive registers) on the PLC without rearranging them, specify the swap parameter in the PI point's Extended Descriptor (ExDesc). Alternatively, use the Modbus Interface Configurator to enable byte swapping for data type 16. This sets the /swap16 configuration file parameter for the PLC, which has the same effect as specifying swap for all points of data type 16.