LAN9730 Datasheet, PDF (73/222 Pages) SMSC Corporation – High-Speed Inter-Chip (HSIC) USB 2.0

LAN9730/LAN9730i
TABLE 4-53: TX CHECKSUM PREAMBLE
Field
31:28
27:16
15:12
11:0
Description
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
bytes of the TX packet.
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 last 4 bytes of the TX packet.
Note:
Note:
Note:
Note:
Note:
Note:
When the TXCOE is enabled, the third DWORD of the pre-pended packet is not transmitted. However, 4
bytes must be added to the packet length field in TX Command B.
Software applications must stop the transmitter and flush the TX data path before changing the state of the
TXCOE_EN bit. However, the CK bit of TX Command B can be set or cleared on a per-packet basis.
The TXCOE_MODE may only be changed if the TX path is disabled. If it is desired to change this value
during run time, it is safe to do so only after the TX Ethernet path is disabled and the TLI is empty.
The TX checksum preamble must be DWORD-aligned.
TX preamble size is accounted for in both the buffer length and packet length.
The first buffer, which contains the TX preamble, may not contain any Ethernet frame data.
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DS00001946A-page 73