RS485 is a multi-drop half-duplex data bus topology where only one node can transmit data and all the other nodes should receive at a given time. Because of the half duplex nature of RS485, transceivers at each node must be properly switched between transmit and receive modes during data transmission and reception respectively. Classical RS232 to RS485 convertors overcome this problem by using flow control signal lines at RS232 side. However, since most of the available hardware and software combinations use only 3 wire RS232 connecitons (Rx, Tx and GND), usage of the flow control lines for this purpose is not the solution in most of the cases.
Teherefore, the real solution to the problem should be an intelligent one wihich follows transmitted data at RS232 side and switches the transceiver respectively.
Semi-automatic convertors contain a control circuit for this purpose. However, timing for switching the transceiver between transmit and receive modes is strongly dependent on the data rate and data format (bit length) being used. This is why the control circuits of semi-automatic convertors require complicated DIP switch combination set-up procedures in order to match the data rate and the data format being used.
"Self-Tuner" is a patented technology solution to this problem where no DIP switch set-up is needed. Using the RS232 / RS485 convertors containing "Self-Tuner" ASIC chips, you only require to connect Rx, Tx and GND lines at RS232 side. RS485 transceiver will be properly switched between transmit and receive modes by automatically adapting to the data rate and data format being used and an excellent and error-free communicaiton will be performed.