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Figure 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 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

22

EMAC/MDIO Module

SPRUFL5B –April 2011

 

 

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Texas Instruments TMS320C674X manual Transmit Buffer Descriptor Format