Altera 40-Gbps Ethernet MAC and PHY MegaCore Function - Manual (Page 84)

packet filtering. The reset state for both bits is 1, where filtering is enabled. The bits are gated by
RX_FILTER_CTRL
bit [0], which enables and disables all filtering.
2. If you have enabled pause packet filtering, the IP core drops packets that enter the RX MAC and match
the length and type of 0x8808 with an opcode of 0x1 (pause packets) and does not process them or
forward them to the client interface.
3. If you have enabled non-pause control packet filtering, the IP core drops packets that enter the RX
MAC and match the length and type of 0x8808 with an opcode other than 0x1 (pause packets) and
does not forward them to the client interface.
4. If you have disabled pause packet filtering, the RX MAC forwards pause packets to the client interface
depending on their destination address. If destination address filtering is not enabled, you are
forwarded all pause packets. If destination address filtering is enabled, you are only forwarded pause
packets with a valid packet multicast address or a destination address matching the 40-100GbE IP core
address.
Pause and control packet pass-through do not affect the pause functionality in the TX or RX MAC.
Related Information
MAC Configuration and Filter Registers on page 3-99
Information about the
RX_FILTER_CTRL
register.
40-100GbE IP Core Modes of Operation
This section explains the cut-through, store and forward, and promiscuous modes of the 40-100GbE IP
core.
In the normal mode of operation, the 40-100GbE IP core MAC transmits and receives data through a
PHY to and from a remote link partner Ethernet MAC. You can program IP core registers to control the
way in which the IP core RX MAC operates.
You can program the RX MAC to selectively filter incoming Ethernet packets based on various criteria.
For example, the RX MAC performs address filtering, various header checking, and control frame
termination according to the IEEE 802.3 standard. You must enable filtering to discard mismatched
destination addresses.
If you choose to accept all incoming Ethernet packets, and not filter on any criterion, except possibly to
filter out runt packets, the IP core is configured in cut-through mode. If you filter based on any criterion
other than runt packets, the IP core is configured in store and forward mode, in which it buffers the
incoming packet for checking before processing in the MAC.
If the IP core is in cut-through mode, it meets the criteria for promiscuous receive mode, as defined in the
Ethernet standard. This definition specifies that the Ethernet implementation accept all valid frames,
regardless of destination address. In cut-through mode, the IP core accepts all Ethernet frames that are
sufficiently well-formed to be identified. Runt frames are invalid frames, according to the Ethernet
standard, and therefore their acceptance or rejection is immaterial to the criteria for promiscuous receive
mode.
Related Information
40-100GbE IP Core RX Filtering on page 3-21
Link Fault Signaling Interface
The 40-100GbE IP core provides link fault signaling as defined in the IEEE 802.3ba-2010 100G Ethernet
Standard. The 40GbE and 100GbE MAC include a Reconciliation Sublayer (RS) located between the
UG-01088
2014.12.15
40-100GbE IP Core Modes of Operation 3-37
Functional Description Altera Corporation
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