Altera 10-Gbps Ethernet MAC MegaCore Function - Manual (Page 153)

February 2014 Altera Corporation 10-Gbps Ethernet MAC MegaCore Function User Guide
A. Frame Format
A.1. Ethernet Frame
Figure A–1 shows the Ethernet frame format.
The Ethernet frame comprises the following fields:
■ Inter-packet gap (IPG)—an average inter-frame length of 12 octets and is
represented with the Idle control character which consists of data value 0x07.
■ Preamble—inserted by the MAC or the client. MAC-inserted preamble is a
maximum of 7 octets of data with value 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.
■ End frame delimiter (EFD)—a 1-octet fixed value of 0xFD which marks the end of
a frame.
Figure A–1. Ethernet Frame Format
Pad (Optional)
Frame Check Sequence
Destination Address
Source Address
MAC Client Length/Type
Payload Data
7 Octets
1 Octets
2 Octets
0..1500/9600 Octets
1 Octets
6 Octets
6 Octets
4 Octets
0..46 Octets
End Frame Delimiter (EFD)
Start Frame Delimite (SFD)
Preamble
Inter-Packet Gap (IPG) 12 Octets
F
rame Length