SPRUIV7B May 2022 – September 2023 AM620-Q1 , AM623 , AM625 , AM625-Q1 , AM625SIP
The Host is ultimately responsible for providing all of the free descriptors and buffers that the port uses as it receives packets. Each entry on the Rx Free Descriptor/Buffer Queue consists of one or more descriptors chained together with each descriptor also pointing to a single contiguous buffer. Each entry on the Rx Free Descriptor/Buffer queue is intended to receive one packet of data. All chaining of descriptors within a packet is performed prior to placing the Rx resources onto the free queues.
Before the Host adds each Rx buffer descriptor chain to the queue, it must first initialize the Rx buffer descriptor values as follows:
Write the Buffer Pointer with the byte aligned address of the buffer data
Write the Buffer Size
Write the next descriptor pointer to the next descriptor in the chain (non-eop) or to 0x0 (eop)
All other fields in the Descriptor do not need to be initialized as they will be overwritten by the Port on reception.