Select baud rate and parity from the drop down list. Click either Master or Slave buttons to select type of operation. Enter timing parameters or address as applicable. Click update to register your changes.

If your slave/server device only supports function codes 5 and 6 for writing, check the Use FC 5/6 box. The default function codes are 15 and 16, which are most widely used. If you check the box, you should also enter a "starting at" unit # or slave address. This allows supporting both types of devices at the same time provided you assign slave addresses in two non-overlapping groups. (These settings do not apply if the SPX is the slave.)

The double register swap on this page only applies when the local device (the gateway you are configuring here) is functioning as a Modbus RTU slave.

The term "swapped" only applies to double or float formats. Modbus registers are, by definition, 16 bits of data per register. Access to 32-bit data, either 32-bit integer ("double"), or IEEE 754 floating point ("float"), is supported by the use of two consecutive registers. Modbus protocol is inherently "big endian", therefore, Modbus by the Module defaults to having the high order register first for double and float. If the low order register comes first on the device being accessed, check the "swapped" box.

If you have "swapped" turned around, you will quickly recognize it. If floating point data is reversed, a 1.0 becomes 2.2779508e-41, which simply rounds to zero. The pattern is not as predictable as the 1.0 example would suggest. A floating point 1.1 becomes negative 107609184. If 32-bit integer data is reversed, 1 becomes 65536.