SPRUHZ7K August 2015 – April 2024 AM5706 , AM5708 , AM5716 , AM5718 , AM5718-HIREL
Buffer Offset
Indicates how many unused bytes are at the start of the buffer. A value of 0000h indicates that there are no unused bytes at the start of the buffer and that valid data begins on the first byte of the buffer. A value of 000Fh (decimal 15) indicates that the first 15 bytes of the buffer are to be ignored by the port and that valid buffer data starts on byte 16 of the buffer. The port writes the Buffer_Offset with the value from the CPDMA_RX_BUFFER_OFFSET register value. The host initializes the Buffer_Offset to zero for free buffers. The Buffer_Length must be greater than the CPDMARX_BUFFER_OFFSET register value. The buffer offset is valid only on SOP.
Buffer Length
Indicates how many valid data bytes are in the buffer. Unused or protocol specific bytes at the beginning of the buffer are not counted in the Buffer Length field. The host initializes the Buffer_Length, but the port may overwrite the host initiated value with the actual buffer length value on SOP and/or EOP buffer descriptors. SOP buffer length values will be overwritten if the packet size is less than the size of the buffer or if the offset is nonzero. EOP buffer length values will be overwritten if the entire buffer is not filled up with data. The Buffer_Length must be greater than zero.