Altera Low Latency Ethernet 10G MAC - Manual (Page 26)

Frame Types
The MAC IP core supports the following frame types:
• Basic Ethernet frames, including jumbo frames.
• VLAN and stacked VLAN frames.
• Control frames, which include pause and PFC frames.
TX Datapath
The MAC TX receives the client payload data with the destination and source addresses, and appends
various control fields depending on the MAC configuration.
Figure 3-3: Typical Client Frame at TX Interface
Client - MAC Tx Interface
(optional)
Client Frame
MAC Frame
Destination
Addr[47:0] Source
Addr[47:0]
Type/
Length[15:0]
Payload
[:0]
Destination
Addr[47:0]
SFD[7:0]
Preamble
[55:0]
CRC32
[31:0]
PAD []
Source
Addr[47:0]
Client-Defined Preamble
[63:0]
(optional)
Type/
Length[15:0]
Payload
[:0]
PAD []
CRC32
[31:0]
EFD[7:0]
IPG
[:0]
Frame Length
(1) (2)
(3)
Padding Bytes Insertion
By default, the MAC TX inserts padding bytes (0x00) into TX frames to meet the following minimum
payload length:
• 46 bytes for basic frames
• 42 bytes for VLAN tagged frames
• 38 bytes for stacked VLAN tagged frames
Ensure that CRC-32 insertion is enabled when padding bytes insertion is enabled.
You can disable padding bytes insertion by setting the
tx_pad_control
register to 0. When disabled, the
MAC IP core forwards the frames to the PHY-side interface without padding. Ensure that the minimum
payload length is met; otherwise the current frame may get corrupted. You can check for undersized
frames by referring to the statistics collected.
Address Insertion
By default, the MAC TX retains the source address received from the client. You can configure the MAC
TX to replace the source address with the primary MAC address specified in the
tx_addrins_macaddr0
and
tx_addrins_macaddr1
registers by setting the bit
tx_src_addr_override[0]
to 1.
3-4 Frame Types
UG-01144
2014.12.15
Altera Corporation Functional Description of LL Ethernet 10G MAC
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