Until now, we have touched topics which involve sending and receiving ASCII data to and from the device. However, sometimes a simpler method is needed. This is true especially in the case of establishing and dropping connections, which is one of the simplest functions of any communication device, and is often used.
Thus, the advanced usage options for the DSR and DTR lines. Correct use of these lines will allow your serial device to find out the current connection status, and control it, without even entering programming mode or sending a single command. See below:
DTR - Detecting Data Connection Status
The DTR Mode (DT) setting controls the behaviour of the DTR line.
Assuming this setting is set to 1 (connection status), the DTR line will be LOW when no data connection is established, and HIGH when a data connection is established. Thus, you can have your serial device directly sense the status of the data connection, without using the Echo (X) command .
DSR - Controlling Data Connection Status
If the Connection Mode (CM) setting is set to 3 (on command or DSR=HI), the DS will establish an outbound data connection whenever the serial device sets the DSR line to HIGH for at least 20ms. This is, of course, only relevant if the Routing Mode [setting /parameter ] is not 0 (when it is 0, the DS will not make an outbound connection).