Depending on which VLEN mode is used, attempting a variable-length transfer with length 0 or 1 can lead
to erroneous behavior by the DMA. The failing conditions do not occur naturally in an application, as they
do not transfer useful data, but may occur as the result of an error condition at the source of the DMA
transfer. The DMA is generally set up with variable transfer length to transfer packets that come in over
USART or RF. If there is an error in the medium, these packets may be malformatted. If, for example, they
contain a length byte of 0, using the DMA to transfer those packets automatically without taking the
described precautions may lead to a buffer overrun. The two VLEN modes that are affected are VLEN
values 001 and 010. VLEN values 000, 011 and 100 work without restrictions.