Altera Triple Speed Ethernet MegaCore Function User Manual Page 192

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A
Ethernet Frame Format
2014.06.30
UG-01008
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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:
Preamblea 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 addresses6 octets each. The least significant byte is transmitted first.
Length or typea 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 Padvariable length data and padding.
Frame check sequence (FCS)a 4-octet cyclic redundancy check (CRC) value for detecting frame errors
during transmission.
An extension fieldRequired 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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