Altera Low Latency Ethernet 10G MAC - Manual (Page 36)

Address Checking
The MAC RX can accept frames with the following address types:
• Unicast address—bit 0 of the destination address is 0.
• Multicast address—bit 0 of the destination address is 1.
• Broadcast address—all 48 bits of the destination address are 1.
The MAC RX always accepts broadcast frames. By default, it also receives all unicast and multicast frames
unless configured otherwise in the
EN_ALLUCAST
and
EN_ALLMCAST
bits of the
rx_frame_control
register.
When the
EN_ALLUCAST
bit is set to 0, the MAC RX filters unicast frames received. The MAC RX accepts
only unicast frames with a destination address that matches the primary MAC address specified in the
primary_mac_addr0
and
primary_mac_addr1
registers. If any of the supplementary address bits are set to
1 (
EN_SUPP0
/
1
/
2
/
3
in the
rx_frame_control
register), the MAC RX also checks the destination address
against the supplementary addresses in the
rx_frame_spaddr*_*
registers.
When the
EN_ALLMCAST
bit is set to 0, the MAC RX drops all multicast frames. This condition does not
apply to global multicast pause frames.
Frame Type Checking
The MAC RX checks the length/type field to determine the frame type:
• Length/type < 0x600—The field represents the payload length of a basic Ethernet frame. The MAC RX
continues to check the frame and payload lengths.
• Length/type >= 0x600—The field represents the frame type.
• Length/type = 0x8100—VLAN or stacked VLAN tagged frames. The MAC RX continues to check
the frame and payload lengths.
• Length/type = 0x8808—Control frames. The next two bytes are the Opcode field which indicates
the type of control frame. For pause frames (Opcode = 0x0001) and PFC frames (Opcode =
0x0101), the MAC RX proceeds with pause frame processing. By default, the MAC RX drops all
control frames. If configured otherwise (
FWD_CONTROL
bit in the
rx_frame_control
register = 1),
the MAC RX forwards control frames to the client.
• For other field values, the MAC RX forwards the receive frame to the client.
Length Checking
The MAC RX checks the frame and payload lengths of basic, VLAN tagged, and stacked VLAN tagged
frames. The MAC RX does not drop frames with invalid length but sets the error bits accordingly.
3-14 Address Checking
UG-01144
2014.12.15
Altera Corporation Functional Description of LL Ethernet 10G MAC
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