The number of FTDI virtual COM ports that may be installed in a system can be limited by setting the MaxDevs parameter. MaxDevs defaults to 0, meaning that the feature is disabled and the driver will always attempt to create a COM port. The default can be overridden by including a non-zero MaxDevs value in the FTDIBUS.INF service key section.
AddReg = FtdiBus.NT.AddService.AddReg
In this example INF file fragment, the maximum number of devices is set to 3.
This value is held in the registry key located at
If an attempt is made to install more than MaxDevs devices, a Code 10 error ("This device cannot start") is generated for the new device.
Note that setting MaxDevs to a value other than zero will radically alter the behaviour of the driver; please contact FTDI if you think you have to change MaxDevs.