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Peripheral Architecture
2.5.4Transmit Buffer Descriptor Format
A transmit (TX) buffer descriptor (Figure 6) is a contiguous block of four
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| Figure 6. Transmit Buffer Descriptor Format | |||
Word 0 |
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31 |
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| 0 |
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| Next Descriptor Pointer |
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Word 1 |
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31 |
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| 0 |
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| Buffer Pointer |
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Word 2 |
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31 |
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| 16 | 15 | 0 |
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| Buffer Offset |
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| Buffer Length | |
Word 3 |
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31 | 30 | 29 | 28 | 27 | 26 | 25 | 16 |
SOP | EOP | OWNER | EOQ | TDOWNCMPLT | PASSCRC |
| Reserved |
15 |
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| 0 |
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| Packet Length |
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Example 1. Transmit Buffer Descriptor in C Structure Format
/*
//EMAC Descriptor
//The following is the format of a single buffer descriptor
//on the EM
AC. |
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*/ |
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typedef struct _EMAC_Desc { |
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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; |
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/* Packet Flags |
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| */ |
#define EMAC_DSC_FLAG_SOP | 0x80000000u |
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#define EMAC_DSC_FLAG_EOP | 0x40000000u |
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#define EMAC_DSC_FLAG_OWNER | 0x20000000u |
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#define EMAC_DSC_FLAG_EOQ | 0x10000000u |
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#define EMAC_DSC_FLAG_TDOWNCMPLT | 0x08000000u |
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#define EMAC_DSC_FLAG_PASSCRC | 0x04000000u |
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20 Ethernet Media Access Controller (EMAC)/SPRU941A
Management Data Input/Output (MDIO) | Submit Documentation Feedback |
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