40.6.3.4 DMA Bursting on the System Bus
When performing data transfers, the system bus burst length used can be programmed using bits 4:0 of the DMA Configuration register.
When there is enough space and enough data to be transferred, the programmed fixed length bursts will be used. If there is not enough data or space available, for example when at the beginning or the end of a buffer, single type accesses are used.
The DMA will not terminate a fixed length burst early, unless an error condition occurs on the system bus or if receive or transmit are disabled in the Network Control register.