ADLINK PCI-7200 - Manual (Page 92)

80 Double Buffer Mode Principle
half-full and ready for copying to the transfer buffer. Then call
_7200_DblBufferTransfer() to copy data from the ready half buffer
to the transfer buffer.
In Windows 95, W_7200_Alloc_DBDMA_Mem() is needed to allo-
cate a contiguous DMA memory for the circular buffer. The
buf_size argument of W_7200_Alloc_DBDMA_Mem() is the half
size of circular buffer in byte, that is, the size of each half buffer in
byte. The DMA memory is referenced by the return parameter
handle. This memory is system memory; users are not allowed to
access it directly.