Posts Tagged ‘CTS’

Different Null Modems

Tuesday, May 27th, 2008

There are several pinout schemes of virtual null modems. Three lines null modem (without handshaking) is simplest where only the data lines are cross connected in the null modem communication. It’s simplest and can’t be used in all circumstances because there is a problem, if either of the two applications checks the DSR or DCD inputs. These signals normally define the ability of the other side to communicate. As they are not connected, their signal level will never go high. This might cause a problem. As you can imagine, with this simple null modem no hardware flow control can be implemented. The only way to perform flow control is with software flow control using the XOFF and XON characters. Virtual Serial Port Kit doesn’t use simplest null modem. (more…)