LAN89218AQ Standard Microsystems (SMSC), LAN89218AQ Datasheet - Page 36

• Manufacturer Part Number: LAN89218AQ
• Manufacturer: Standard Microsystems (SMSC)

Specifications of LAN89218AQ

• Lead Free Status / RoHS Status: Compliant

Revision 1.3 (02-23-10)
3.6.2.1
FIELD
31:28
27:16
15:12
11:0
An example of a TX packet with a pre-pended TX checksum preamble can be found in
3.12.6.3, "TX Example
four fragments, the first containing the TX Checksum Preamble.
fragments are loaded into the TX Data FIFO. For more information on the TX Command ‘A’ and TX
Command ‘B’, refer to
If the TX packet already includes a partial checksum calculation (perhaps inserted by an upper layer
protocol), this checksum can be included in the hardware checksum calculation by setting the TXCSSP
field in the TX checksum preamble to include the partial checksum. The partial checksum can be
replaced by the completed checksum calculation by setting the TXCSLOC pointer to point to the
location of the partial checksum.
Note: When the TXCOE is enabled, the third DWORD of the pre-pended packet is not transmitted.
Note: The TX checksum preamble must be DWORD-aligned (i.e., the two least significant bits of the
Note: Software applications must stop the transmitter and flush the TX data path before changing the
TX Checksum Calculation
The TX checksum calculation is performed using the same operation as the RX checksum shown in
Section
transmitted checksum is the one’s-compliment of the final calculation.
RESERVED
TXCSLOC - TX Checksum Location
This field specifies the byte offset where the TX checksum will be inserted in the TX packet. The
checksum will replace two bytes of data starting at this offset.
Note: The TX checksum cannot be inserted in the MAC header (first 14 bytes) or in the last 4
RESERVED
TXCSSP - TX Checksum Start Pointer
This field indicates start offset, in bytes, where the checksum calculation will begin in the associated
TX packet.
Note: The data checksum calculation must not begin in the MAC header (first 14 bytes) or in the
However, 4 bytes must be added to the packet length field in TX Command ‘B’.
Data Start Offset fields in TX Command “A” must be zero). Any valid buffer end alignment
setting can be used.
state of the TXCOE_EN bit. However, the CK bit of TX Command ‘B’ can be set or cleared on
a per-packet basis.
3.6.1.1, with the exception that the calculation starts as indicated by the preamble, and the
bytes of the TX packet.
last 4 bytes of the TX packet.
Section 3.12.2, "TX Command
3". In this example the host writes the packet data to the ethernet controller in
Table 3.7 TX Checksum Preamble
High Performance Single-Chip 10/100 Ethernet Controller for Automotive Applications
DATASHEET
36
DESCRIPTION
Format".
Figure 3.24
shows how these
SMSC LAN89218
Datasheet
Section