WG82574L S LBA8 Intel, WG82574L S LBA8 Datasheet - Page 205

• Manufacturer Part Number: WG82574L S LBA8
• Manufacturer: Intel

Specifications of WG82574L S LBA8

• Operating Supply Voltage (typ): 3.3V
• Operating Temp Range: 0C to 85C
• Operating Temperature Classification: Commercial
• Mounting: Surface Mount
• Pin Count: 64
• Lead Free Status / RoHS Status: Compliant

System Manageability—82574 GbE Controller
8.5
8.6
Receive TCO Flow
The 82574 is used as a channel for receiving packets from the network link and passing
them to the external MC. The MC configures the 82574 to pass these specific packets to
the MC. Once a full packet is received from the link and identified as a manageability
packet that should be transferred to the MC, the 82574 starts the receive TCO flow to
the MC.
The 82574 uses the SMBus notification method to notify the MC that it has data to
deliver. Since the packet size might be larger than the maximum SMBus fragment size,
the packet is divided into fragments, where the 82574 uses the maximum fragment
size allowed in each fragment (configured via the NVM). The last fragment of the
packet transfer is always the status of the packet. As a result, the packet is transferred
in at least two fragments. The data of the packet is transferred as part of the receive
TCO LAN packet transaction.
When SMBus alert is selected as the MC notification method, the 82574 notifies the MC
on each fragment of a multi fragment packet. When asynchronous notify is selected as
the MC notification method, the 82574 notifies the MC only on the first fragment of a
received packet. It is the MC's responsibility to read the full packet including all the
fragments.
Any timeout on the SMBus notification results in discarding the entire packet. Any
NACK by the MC causes the fragment to be re-transmitted to the MC on the next
Receive Packet command.
The maximum size of the received packet is limited by the 82574 hardware to 1536
bytes. Packets larger then 1536 bytes are silently discarded. Any packet smaller than
1536 bytes is processed by the 82574.
Transmit TCO Flow
The 82574 is used as the channel for transmitting packets from the external MC to the
network link. The network packet is transferred from the MC over the SMBus and then,
when fully received by the 82574, is transmitted over the network link.
The 82574 supports packets up to an Ethernet packet length of 1536 bytes. Since
SMBus transactions can only be up to 240 bytes in length, packets might need to be
transferred over the SMBus in more than one fragment. This is achieved using the F
and L bits in the command number of the transmit TCO packet Block Write command.
When the F bit is set, it is the first fragment of the packet. When the L bit is set, it is
the last fragment of the packet. When both bits are set, the entire packet is in one
fragment. The packet is sent over the network link, only after all its fragments are
received correctly over the SMBus. The maximum SMBus fragment size is defined
within the NVM and cannot be changed by the MC.
If the packet sent by the MC is larger than 1536 bytes, than the packet is silently
discarded by the 82574. The minimum packet length defined by the 802.3 spec is 64
bytes. The 82574 pads packets that are less than 64 bytes to meet the specification
requirements (there is no need for the external MC to pad packets less than 64 bytes).
If the packet sent by the MC is larger than 1536 bytes the 82574 silently discards the
packet.
The 82574 calculates the L2 CRC on the transmitted packet and adds its four bytes at
the end of the packet. Any other packet field (such as XSUM) must be calculated and
inserted by the MC (the 82574 does not change any field in the transmitted packet,
other than adding padding and CRC bytes).
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