Altera Triple Speed Ethernet MegaCore Function - Manual (Page 192)

A Ethernet Frame Format
2014.06.30
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Basic Frame Format
Figure A-1: MAC Frame Format
7 octets PREAMBLE
1 octet SFD
6 octets DESTINATION ADDRESS
6 octets SOURCE ADDRESS
2 octets
0..1500 /9600 octets PAYLOAD DATA
0..46 octets PAD
4 octets FRAME CHECK SEQUENCE
EXTENSION
Frame length
(half duplex only)
LENGTH/TYPE
A basic Ethernet frame comprises the following fields:
• Preamble—a maximum of 7-octet fixed value of 0x55.
• Start frame delimiter (SFD)—a 1-octet fixed value of 0xD5 which marks the beginning of a frame.
• Destination and source addresses—6 octets each. The least significant byte is transmitted first.
• Length or type—a 2-octet value equal to or greater than 1536 (0x600) indicates a type field. Otherwise,
this field contains the length of the payload data. The most significant byte of this field is transmitted
first.
• Payload Data and Pad—variable length data and padding.
• Frame check sequence (FCS)—a 4-octet cyclic redundancy check (CRC) value for detecting frame errors
during transmission.
• An extension field—Required only for gigabit Ethernet operating in half-duplex mode. The MAC function
does not support this implementation.
VLAN and Stacked VLAN Frame Format
The extension of a basic MAC frame is a virtual local area network (VLAN) tagged frame, which contains
an additional 4-byte field for the VLAN tag and information between the source address and length/type
ISO
9001:2008
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