The key component of CDM is a new driver that supports D2XX and FTDIBUS class interfaces. The combined driver replaces FTD2XX and FTDIBUS, and an application can use either interface, although not both simultaneously.
A feature of the newer FTDI devices (FT232R, FT245R and FT2232) is a configuration setting held in EEPROM that indicates what type of driver should be loaded for the device, thus determining the device type. This setting is read when the device is enumerated and determines whether a COM port is exposed or not. For example, if a device is programmed as D2XX then no COM port will be exposed for that device. In the case of older FTDI devices (AM and BM series) where there is not an EEPROM setting for driver type, a serial port will be exposed by default. This is to ensure compatibility with existing applications which could use either the D2XX or FTSER2K interface.
The EEPROM settings can be overridden by changing the driver INF files or by changing the "Load VCP" option on the Advanced tab of the USB Serial Converter property page (see ). Please note that CDM 2.00.00 is Microsoft WHQL certified and changing any of the files in the driver package, including INF and INI files, invalidates the certification.