Altera Low Latency 40-Gbps Ethernet MAC and PHY MegaCore Function - Manual (Page 64)

Control Frame Identification
The mechanisms to process flow control frames from the Ethernet link are specific to the flow control
mode of the LL 40-100GbE IP core. Therefore, control frames that are inappropriate to the IP core mode,
simply pass through the RX MAC to the RX client interface.
If you turn off flow control by setting Flow control mode to the value of No flow control in the LL
40-100GbE parameter editor, the IP core might nevertheless receive a flow control request on the Ethernet
link. Similarly, if you set Flow control mode to Standard flow control, the IP core might nevertheless
receive a priority-based flow control request on the Ethernet link, and if you set Flow control mode to
Priority-based flow control, the IP core might nevertheless receive a standard flow control request.
The IP core provides a three-bit RX status flag that identifies the control frames that appear on the RX
client interface. The flag is one-hot encoded to identify whether the control frame is a standard flow
control frame, a priority-based flow control frame, or a different type of control frame. If the flag has the
value of 3'b000, the current packet on the RX client interface is not a control frame. You can use this flag
to identify control frames on the RX client interface that the client prefers to ignore.
Related Information
• Low Latency 40-100GbE IP Core RX Data Bus on page 3-20
• Low Latency 40-100GbE IP Core RX Data Bus Without Adapters (Custom Streaming Interface) on
page 3-24
Low Latency 40-100GbE IP Core RX Data Bus Interface
This section describes the RX data bus at the user interface and includes the following topics:
Low Latency 40-100GbE IP Core User Interface Data Bus on page 3-6
Low Latency 40-100GbE IP Core RX Data Bus on page 3-20
Low Latency 40-100GbE IP Core RX Data Bus Without Adapters (Custom Streaming Interface) on
page 3-24
Low Latency 40-100GbE IP Core User Interface Data Bus
Table 3-4: User Interface Width Depends on IP Core Variation
The Low Latency 40-100GbE IP core provides two different client interfaces: the Avalon-ST interface and a
custom interface. The Avalon-ST interface requires adapters and the custom streaming interface does not require
adapters.
Client Interface
Data Bus Width (Bits)
LL 40GbE IP Core LL 100GbE IP Core
Custom streaming interface (no
adapters)
128 256
Avalon-ST interface (with
adapters)
256 512
UG-01172
2015.05.04
Control Frame Identification 3-19
Functional Description Altera Corporation
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