IMPORTANT: Set timeout to something long enough for the device. If too short, the gateway will not wait
long enough for a response from the Modbus slave device, and the result will be a lot of "no response"
errors from the device even though the device is perfectly functional.
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 BB2-7010 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.
5.2 Modbus RTU Master Read Maps
Rule number simply tells you where you're at on the list of register maps. Click "next" and "prev" to scroll
through the list. To advance directly to a specific map, enter the desired number in the "Showing" box,
then click Update.
5. Configuring BB2-7010 as a Modbus RTU Master
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