Usage of function "USBD_MSC0_SetMediaOwnerFS()"

Hello,

I've ported an example for an Infineon Evalboard to the MBC4300 Evalboard. The example shows how to access the SD-Card file system either via USB host or from the uController.

http://www.keil.com/appnotes/docs/apnt_273.asp

This example seems to work as expected on my MBC4300, I can access the SD-Card from PC Host and the uController can write files onto the SD-Card.
I want to use a similar case in my application, but something does not work as expexted, so I went back to the example code to look at some details using the debugger.

// original code from the example:
case DEV_START_RECORD:
        // hide logical unit
/*B1*/     USBD_MSC0_SetMediaOwnerFS();
        finit("M0:");
        fmount("M0:");
        f_but = fopen("ButtonsLog.txt","a");
        f_adc = fopen("AdcLog.txt","a");
        ADC_StartConversion();
        gState = DEV_RECORDING;
        break;

This code should change the ownership to the uController and create two files.

Condition 1: NO USB-Cable is attached
When I set a breakpoint at B1 and step over the function "USBD_MSC0_SetMediaOwnerFS()" it takes ~3 seconds (timeout defined inside the function)
After the call the Variable "usbd_msc0_media_own" is 2 which means a change is requested (and still pending).
Function returns USBD_MSC0_ERROR.
The following functions (finit, fmount, fopen) do NOT fail although the ownership is not granted.

Condition 2: USB-Cable IS attached
Function returns "USBD_MSC0_OK" after <1sec.
After the call the Variable "usbd_msc0_media_own" is 0

I would expect the opposite behavior.

I don't have the Infineon Evalboard so I cannot test the original unmodified example.
Is it possible that I made a mistake when I ported the example?

Is there a more detailed documentation available about the functions USBD_MSC0_SetMediaOwnerFS() and USBD_MSC0_SetMediaOwnerUSB()

e.g.:
Does it automatically close open files when ownership is changed from FS to USB?
Would it reject a change from USB to FS when the USB-host accesses the SD-Card?
Would it allow a change from USB to FS when the USB-cable is plugged in but USB-host does NOT access athe SD-card?
Thank you.