Architecture
1824
SPNU563A – March 2018
Copyright © 2018, Texas Instruments Incorporated
EMAC/MDIO Module
Example 32-2. Receive Buffer Descriptor in C Structure Format (continued)
#define EMAC_DSC_FLAG_UNDERSIZED 0x00400000u
#define EMAC_DSC_FLAG_CONTROL 0x00200000u
#define EMAC_DSC_FLAG_OVERRUN 0x00100000u
#define EMAC_DSC_FLAG_CODEERROR 0x00080000u
#define EMAC_DSC_FLAG_ALIGNERROR 0x00040000u
#define EMAC_DSC_FLAG_CRCERROR 0x00020000u
#define EMAC_DSC_FLAG_NOMATCH 0x00010000u
32.2.6.5.3 Buffer Offset
This 16-bit field must be initialized to 0 by the software application before adding the descriptor to a
receive queue.
Whether or not this field is updated depends on the setting of the RXBUFFEROFFSET register. When the
offset register is set to a nonzero value, the received packet is written to the packet buffer at an offset
given by the value of the register, and this value is also written to the buffer offset field of the descriptor.
When a packet is fragmented over multiple buffers because it does not fit in the first buffer supplied, the
buffer offset only applies to the first buffer in the list, which is where the start of packet (SOP) flag is set in
the corresponding buffer descriptor. In other words, the buffer offset field is only updated by the EMAC on
SOP descriptors.
The range of legal values for the BUFFEROFFSET register is 0 to (Buffer Length – 1) for the smallest
value of buffer length for all descriptors in the list.