Good morning I have a modbus gateway ab7702 but I don’t know wich terminal is A and B
I have vlf with rs485 positive and negative pins
Modbus gateway ab7702 A and B is terminal A positive ?
What happens if I connect the cables backwards?
The EIA RS-485 Specification labels the data wires “A” and “B”, but some manufacturers label their wires “+” and “-”.
Usually the “-” wire should be connected to the “A” line, and the “+” wire to the “B” line. Reversing the polarity will not damage a 485 device, but it will not communicate, so if it’s not working try switching them.