WG82574L S LBA9 Intel, WG82574L S LBA9 Datasheet - Page 167

• Manufacturer Part Number: WG82574L S LBA9
• Description: CONTROLLER, ENET, INTEL 82574L, 64PQFN
• Manufacturer: Intel

Specifications of WG82574L S LBA9

• Ethernet Type: IEEE 802.3, IEEE 802.3u, IEEE 802.3ab
• Supply Voltage Range: 3V To 3.6V
• Operating Temperature Range: 0°C To +85°C
• Digital Ic Case Style: QFN
• No. Of Pins: 64
• Package / Case: QFN
• Interface Type: I2C, JTAG, PCI, SPI
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Inline Functions—82574 GbE Controller
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7.2.10.3
IPCSS - IP Checksum Start - Specifies the byte offset from the start of the DMA'd data
to the first byte to be included in the checksum. Setting this value to 0b means the first
byte of the data would be included in the checksum. This field is limited to the first 256
bytes of the packet and must be less than or equal to the total length of a given packet.
If this is not the case, the results are unpredictable.
IPCSO - IP Checksum Offset - Specifies where the resulting checksum should be
placed. This field is limited to the first 256 bytes of the packet and must be less than or
equal to the total length of a given packet. If this is not the case, the checksum is not
inserted.
IPCSE - IP Checksum End - Specifies where the checksum should stop. A 16-bit value
supports checksum off loading of packets as large as 64 KB. Setting the IPCSE field to
all zeros means EOP. In this way, the length of the packet does not need to be
calculated.
When doing checksum or TCP segmentation with IPv6 headers IPCSE field should be
set to 0x0000, IPCSS should be valid as in IPv4 packet and the IXSM bit in the data
descriptor should be cleared.
For proper IP checksum calculation, the IP Header Checksum field should be set to zero
unless some adjustment is needed by the driver.
Similarly, TUCSS, TUCSO, TUCSE specify the same parameters for the TCP or UDP
checksum.
For proper TCP/UDP checksum calculation the TCP/UDP Checksum field should be set to
the partial pseudo-header checksum value.
In case of 802.1Q header, the offset values depend on the VLAN insertion enable bit -
CTRL.VME. When the CTRL.VME is not set (VLAN tagging included in the packet
buffers), the offset values should include the VLAN tagging. When the CTRL.VME is set
(VLAN tagging is taken from the packet descriptor), the offset values should exclude
the VLAN tagging.
When setting the TCP segmentation context, IPCSS and TUCSS are used to indicate the
start of the IP and TCP headers respectively, and must be set even if checksum
insertion is not desired.
In certain situations, software might need to calculate a partial checksum (the TCP
pseudo-header for instance) to include bytes that are not contained within the range of
start and end. If this is the case, this partial checksum should be placed in the packet
data buffer, at the appropriate offset for the checksum. If no partial checksum is
required, software must write a value of zero at this offset.
Max Segment Size - MSS
MSS controls the maximum segment size. This specifies the maximum TCP or UDP
payload segment sent per frame, not including any header. The total length of each
frame (or section) sent by the TCP segmentation mechanism (excluding 802.3ac
tagging and Ethernet CRC) is MSS bytes + HRDLEN. The one exception is the last
packet of a TCP segmentation that might be shorter. This field is ignored if TDESC.TSE
is not set.
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