LAN9250 datasheet(168/421 Pages) MICROCHIP

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LAN9250

DS00001913A-page 168

 2015 Microchip Technology Inc.

11.11.6.3

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 “Data Start Offset”

• 4-Byte Checksum Preamble

• 16-Byte “Buffer End Alignment”

Buffer 1:

• 7-Byte “Data Start Offset”

• 79-Bytes of payload data

• 16-Byte “Buffer End Alignment”

Buffer 2:

• 0-Byte “Data Start Offset”

• 15-Bytes of payload data

• 16-Byte “Buffer End Alignment”

Buffer 3:

• 10-Byte “Data Start Offset”

• 17-Bytes of payload data

• 16-Byte “Buffer End Alignment”

Figure 11-12, "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

‘B’ must be set in conjunction with bit 13 (FS) of TX Command ‘A’ and the TX Checksum Offload Engine

Enable (TX_COE_EN) bit of the Host MAC Checksum Offload Engine Control Register (HMAC_COE_CR).

For more information, refer to Section 11.8, "Transmit Checksum Offload Engine (TXCOE)".

LAN9250 Datasheet(PDF) 168 Page - Microchip Technology