RS-485 circuit and communication system

The invention discloses an RS-485 circuit and a communication system. The RS-485 circuit is disposed in an electronic device including a processing module. The RS-485 circuit comprises an RS-485 interface chip, a starting detector, an internal integrated circuit bus and a counter; the default state of the RS-485 interface chip is a data receiving state and comprises a data input end and an enabling end, the data input end is used for receiving a data signal from the processing module, and the enabling end is used for enabling the RS-485 interface chip to be in a data sending state or a data receiving state after receiving a starting signal or a switching signal; the starting detector is used for detecting a first signal edge of the data signal to generate a starting signal to the enabling end; a count value from the processing module is stored in the register through the internal integrated circuit bus, so that the counter counts based on the count value and outputs a switching signal to the enabling end when