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Architecture

Figure 31-7. Transmit Buffer Descriptor Format

Word 0

31 0

Next Descriptor Pointer

Word 1

31 0

Buffer Pointer

Word 2

31 16 15 0

Buffer Offset Buffer Length

Word 3

31 30 29 28 27 26 25 16

SOP EOP OWNER EOQ TDOWNCMPLT PASSCRC Reserved

15 0

Packet Length

Example 31-1. Transmit Buffer 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

1537

SPNU562–May 2014 EMAC/MDIO Module

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