15.3.3.7.2 Receive Descriptor Acquisition
The Receive Engine always attempts to acquire an extra descriptor in anticipation of an incoming frame. Descriptor acquisition is attempted if any of the following conditions is satisfied:
- The SR bit of the EMACDMAOPMODE register has been set immediately after being placed in the RUN state.
- The data buffer or current descriptor is full before the frame ends for the current transfer.
- The controller has completed frame reception, but the current receive descriptor is not yet closed.
- The receive process has been suspended because of a host-owned buffer (RDES0[31] = 0) and a new frame is received.
- A receive poll demand has been issued.