LAN9500 Datasheet, PDF (54/213 Pages) SMSC Corporation – USB 2.0 to 10/100 Ethernet Controller Promiscuous mode

LAN950x
Note:
When enabled, the TX Checksum Preamble is pre-pended to the data to be transmitted. The FS bit in TX
Command A, the TX Checksum Enable bit (CK) of TX Command B, and the TXCOE_EN bit of the
COE_CR register must all be set for the TX checksum to be generated. FS must not be set for subsequent
fragments of the same packet. Please refer to Section 5.5.8, "Transmit Checksum Offload Engine
(TXCOE)" for further information.
FIGURE 5-8:
TX EXAMPLE 3
.
.
.
TX Command B
TX Command A
USB Packet 0
115 Byte
Ethernet
Frame
17 Byte Payload
TX Command B
TX Command A
15 Byte Payload
TX Command B
TX Command A
79 Byte Payload
TX Command B
TX Command A
Checksum Preamble
TX Command B
TX Command A
DS00001875A-page 54
TX Command A
Data Start Offset = 2
First Segment = 0
Last Segment = 1
Buffer Size = 17
TX Command A
Data Start Offset = 0
First Segment = 0
Last Segment = 0
Buffer Size = 15
TX Command B
Frame Length = 111
TX Checksum Enable = 1
TX Command B
Frame Length = 111
TX Checksum Enable = 1
TX Command A
Data Start Offset = 3
First Segment = 0
Last Segment = 0
Buffer Size = 79
TX Command A
Data Start Offset = 0
First Segment = 1
Last Segment = 0
Buffer Size = 4
TX Command B
Frame Length = 111
TX Checksum Enable = 1
TX Command B
Frame Length = 111
TX Checksum Enable = 1
Checksum Preamble
TX Checksum Location = 50
TX Checksum Start Pointer = 14
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