Texas Instruments TMS320DM36X manual Transmit Buffer Descriptor Format

Models: TMS320DM36X

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Architecture

2.6.4Transmit Buffer Descriptor Format

A transmit (TX) buffer descriptor (Figure 6) 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 1 shows the transmit buffer descriptor described by a C structure.

 

 

 

 

Figure 6. 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

SPRUFI5B –March 2009 –Revised December 2010 Ethernet Media Access Controller (EMAC)/Management Data Input/Output 23

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Texas Instruments TMS320DM36X manual Transmit Buffer Descriptor Format