LAN9500 Datasheet, PDF (53/213 Pages) SMSC Corporation – USB 2.0 to 10/100 Ethernet Controller Promiscuous mode

LAN950x
5.4.2.8 TX Example 2
In this example, a single 183-Byte Ethernet frame will be transmitted. This packet is in a single buffer as follows:
• 2-Byte “Data Start Offset”
• 183-Bytes of payload data
FIGURE 5-7: TX Example 2 on page 53 illustrates the TX command structure for this example, and also shows how
data is passed to the TX data FIFO. Note that the packet resides in a single TX Buffer, therefore both the FS and LS
bits are set in TX Command A.
FIGURE 5-7:
TX EXAMPLE 2
USB Packet 0
.
.
.
TX Command B
TX Command A
183 Byte Payload
TX Command B
TX Command A
TX Command A
Data Start Offset = 2
First Segment = 1
Last Segment = 1
Buffer Size = 183
TX Command B
Frame Length = 183
183 Byte
Ethernet
Frame
5.4.2.9 TX Example 3
In this example a single, 111-Byte Ethernet frame will be transmitted with a TX checksum. This packet is divided into
four buffers. The four buffers are as follows:
Buffer 0:
• 0-Byte “Data Start Offset”
• 4-Byte Checksum Preamble
Buffer 1:
• 3-Byte “Data Start Offset”
• 79-Bytes of payload data
Buffer 2:
• 0-Byte “Data Start Offset”
• 15-Bytes of payload data
Buffer 3:
• 2-Byte “Data Start Offset”
• 17-Bytes of payload data
FIGURE 5-8: TX Example 3 on page 54 illustrates the TX command structure for this example, and also shows how
data is passed to the TX data FIFO.
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DS00001875A-page 53