Texas Instruments TMS320DM646x 사용자 설명서
www.ti.com
2.5.4
Transmit Buffer Descriptor Format
Architecture
A transmit (TX) buffer descriptor (
) is a contiguous block of four 32-bit data words aligned on a
32-bit boundary that describes a packet or a packet fragment.
shows the transmit buffer
descriptor described by a C structure.
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
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
24
Ethernet Media Access Controller (EMAC)/Management Data Input/Output (MDIO)
SPRUEQ6 – December 2007