Differences to COM

  • Interval Timeout
    The virtual COM port for an EL60xx bus terminal does not support interval timeouts, because the driver has no access to the required information
  • DSR/DTR Handshake
    EL6001 and EL6021 do not have DSR/DTR lines
  • Explicit Setting of RTS/CTS lines
    The explicit setting of RTS and CTS lines is not supported.
  • XON/XOFF char cannot be changed
    The EL6001/EL6021 has fixed values for XON and XOFF characters, i.e. 0x11 and 0x13, respectively. These cannot be changed.

 

On TwinCAT stop all virtual COM ports created by the TcEL60xx driver on this computer are removed. A TwinCAT start creates the virtual COM port defined by the current configuration. So an application, which had opened a COM port, has to open it again, after a TwinCAT re-start. An application, which uses one of the virtual COM ports, must close this port before the TwinCAT stop, because in general it is undefined how an application will handle the removal of an open COM port.

 

Virtual COM Port on Remote Computer

Suppose that an EL60xx bus terminal is connected to computer A, while the associated virtual COM port is created on computer B. The driver handles TwinCAT start and stop as follows:

TwinCAT stop on computer A breaks the connection to the bus terminal while the virtual COM port on computer B persists. Read and write request for the virtual COM port on computer B would fail. A successive TwinCAT start on computer A again creates the virtual COM on computer B. Using the AMS address the EL60xx driver on computer B checks, if a virtual COM port for this address exists and removes it respectively. Then the virtual COM port is created, possibly with another number, which could be changed within System Manager.

 

TwinCAT Stop on computer B removes all virtual COM ports on this computer. After TwinCAT start on computer B virtual COM ports can be created again. However, the virtual COM port, which was created from computer A, will not be available. Not until the TwinCAT on computer A has been restarted the virtual COM port on computer B is created again.

As the TwinCAT on computer B will not be notified when the TwinCAT on computer A is stopped, it is not possible to remove the virtual COM port. If the configuration on computer A is changed, e.g. such that no virtual COM port is created, then an orphaned virtual COM port on computer B persists until the next TwinCAT stop on this computer.

Requirements

Development environment

Target system type

TwinCAT v3.0.0

PC or CX (x86)