Solution:

We can use the both DMA channels by switch the channel by software on this card. However, data will lost during this switching period. Plus, the performance was less than just using single DMA channel. Besides, only PCL-1800 support the hardware dual DMA channels feature. That card switch the DMA channel automatically by hardware, so the switching time is very short to meet the high performance application. Anyway, it's recommended to use the FIFO and interrupt feature for the high speed application. In fact the FIFO will generate an interrupt while FIFO is half-full or full to receive the data. And during the transfer period (FIFO half-full or full event), the FIFO will receive the data continuously without any data lost!