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LAN9221_12 Datasheet, PDF (59/151 Pages) SMSC Corporation – High-Performance 16-bit Non-PCI 10/100 Ethernet Controller with Variable Voltage I/O | |||
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High-Performance 16-bit Non-PCI 10/100 Ethernet Controller with Variable Voltage I/O
Datasheet
3.12.6.3
TX Example 3
In this example a single, 111-Byte Ethernet packet will be transmitted with a TX checksum. This packet
is divided into four buffers. The four buffers are as follows:
Buffer 0:
 4-Byte âData Start Offsetâ
 4-Byte Checksum Preamble
 16-Byte âBuffer End Alignmentâ
Buffer 1:
 7-Byte âData Start Offsetâ
 79-Bytes of payload data
 16-Byte âBuffer End Alignmentâ
Buffer 2:
 0-Byte âData Start Offsetâ
 15-Bytes of payload data
 16-Byte âBuffer End Alignmentâ
Buffer 3:
 10-Byte âData Start Offsetâ
 17-Bytes of payload data
 16-Byte âBuffer End Alignmentâ
Figure 3.21, "TX Example 1" illustrates the TX command structure for this example, and also shows
how data is passed to the TX data FIFO.
Note:
In order to perform a TX checksum calculation on the associated packet, bit 14 (CK) of the TX
Command âBâ must be set in conjunction with bit 13 (FS) of TX Command âAâ and bit 16
(TXCOE_EN) of the COE_CR register. For more information, refer to Section 3.6.2, "Transmit
Checksum Offload Engine (TXCOE)".
SMSC LAN9221/LAN9221i
59
DATASHEET
Revision 2.9 (03-01-12)
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