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EMAC Functional Architecture
2.5.5 Receive Buffer Descriptor Format
A receive (RX) buffer descriptor (Figure 13) is a contiguous block of four 32-bit data words aligned on a
32-bit boundary that describes a packet or a packet fragment.
Example 2 shows the receive descriptor described by a C structure.
Figure 13. Receive Descriptor Format
(a) Word 0
31 0
Next Descriptor Pointer
(b) Word 1
31 0
Buffer Pointer
(c) Word 2
31 16 15 0
Buffer Offset Buffer Length
(d) Word 3
31 30 29 28 27 26 25 24
SOP EOP OWNER EOQ TDOWNCMPLT PASSCRC JABBER OVERSIZE
23 22 21 20 19 18 17 16
FRAGMENT UNDERSIZED CONTROL OVERRUN CODEERROR ALIGNERROR CRCERROR NOMATCH
15 0
Packet Length
Example 2. Receive Descriptor in C Structure Format
/*
// EMAC Descriptor
//
// The following is the format of a single buffer descriptor
// on the EMAC.
*/
typedef struct _EMAC_Desc {
struct _EMAC_Desc *pNext; /* Pointer to next descriptor in chain */
Uint8 *pBuffer; /* Pointer to data buffer */
Uint32 BufOffLen; /* Buffer Offset(MSW) and Length(LSW) */
Uint32 PktFlgLen; /* Packet Flags(MSW) and Length(LSW) */
} EMAC_Desc;
/* Packet Flags */
#define EMAC_DSC_FLAG_SOP 0x80000000u
#define EMAC_DSC_FLAG_EOP 0x40000000u
#define EMAC_DSC_FLAG_OWNER 0x20000000u
#define EMAC_DSC_FLAG_EOQ 0x10000000u
#define EMAC_DSC_FLAG_TDOWNCMPLT 0x08000000u
#define EMAC_DSC_FLAG_PASSCRC 0x04000000u
#define EMAC_DSC_FLAG_JABBER 0x02000000u
#define EMAC_DSC_FLAG_OVERSIZE 0x01000000u
#define EMAC_DSC_FLAG_FRAGMENT 0x00800000u
#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
37
SPRUEF8F–March 2006–Revised November 2010 C6472/TCI6486 EMAC/MDIO
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