Bus Master Transfer

Bus Master Transfer is one of the function of PCI Express bus or PCI bus. Input/output is performed directly from board to user's memory without CPU's interveneing.
If this function is used, the internal timer of the device and so on can be used, then high-speed input/output can be performed exactly.
Bus Master Transfer is that CPU uses the time which bus is not used, and the transfer from board to memory of personal computer is not performed.
The load of system becomes to be high. If the device cannot acquire bus, transfer error will occur.

You can confirm the status of transfer error by the 4th argument Err on DioDmGetStatus function.