Serial Device Firmware Upgrade

Dear Tech Gurus,
My intention is to perform a DFU(Device
Firmware Upgrade) with a WinCE PDA Host for a serial
interface.
I bring my device from the functional Firmware Mode to
the BootROM mode using my Vendor IOCTL. Now the device is
detached from the functional firmware to the BOOTROM mode
(meaning to say I have detached my drivers)
Now I open the serial port(COM4:) by CreateFile API. I
get a success in opening the Serial Port
When I issue a ReadFileCommand the application hangs and
to revert I will have to give a soft reset
My inference is that the ReadFile fails when the firmware
is in the BootRom mode
Can any one suggest a workaround or a solution to the
above problem.

Thanks in advance,

Cheers,
Lakshman