Modem building Chain Process details

Terminal MODEM

Step 1| dtr-->|

Step 2| txd-->|

Step 3|<--dsr|

Step 4|<--dcd|

Step 5|<--cts|

Step 6|<--rxd|

1, from the terminal to send the DTR signal to the MODEM,DTR signal by the RS232 DTR Foot sent out, tell the modem terminal is ready;

2, the terminal sent TXD signal to the modem, the terminal by RS232 Txd sent a signal to the modem has been kept in logic 1, it is not data, but a handshake signal, this signal tells the modem, the terminal to communicate with each other. If the modem is ready, then the modem will be RS232 through the RXD signal line to maintain logic 1 to tell the terminal modem is ready to use the modem to dial. At this time there is no data between the terminal and modem transmission;

3, by the modem to send the DSR to the terminal, when the dial is completed, the modem issued a DSR signal to the terminal, the modem has been with the remote modem to make a good connection preparation, that is, the modem is waiting for the remote modem back information;

4, the modem sent to DCD to the terminal, when the modem and the remote modem to complete the handshake, the modem back to the DCD signal to the terminal, indicating that the modem has established a connection;

5, the modem to send CTS to the terminal, the completion of the above process, the terminal still can not receive and send data, must wait until the modem sent CTS signal, said all ready;

6, the modem transmits data to the terminal, the terminal begins to receive or sends the data.

*: The communication process through the Rts/cts hardware flow control, through the Xon/xoff software flow control.