K60P100M100SF2RM Datasheet, PDF (1202/1809 Pages) Freescale Semiconductor, Inc – K60 Sub-Family Reference Manual

Functional Description
The frame fragment status bit, RxBD[FRAG], is set to indicate a fragment reception and
the one's-complement sum of the IP payload is available in RxBD[Payload checksum].
Note
The application software can take advantage of the payload
checksum delivered with the frame's status word to calculate
the protocol-specific checksum of the datagram after all
fragments have been received and reassembled.
For example, if a TCP payload is delivered by multiple IP fragments, the application
software can calculate the pseudo-header checksum value from the first fragment and add
the payload checksums delivered with the status for all fragments to verify the TCP
datagram checksum.
44.4.8.6 IPv6 Support
The following sections describe the IPv6 support.
44.4.8.6.1 Receive Processing
An Ethernet frame of type 0x86DD identifies an IP Version 6 frame (IPv6) frame. If an
IPv6 frame is received, the first IP header is inspected (first ten words) which is available
in every IPv6 frame.
If the receive SHIFT16 function is enabled, the IP header is aligned on a 32-bit boundary
allowing more efficient processing (see 32-bit Ethernet Payload Alignment).
For TCP and UDP datagrams the pseudo-header checksum calculation is performed and
verified.
To assist in protocol-specific checksum verification, the one's-complement sum is always
calculated on the IP payload (all bytes following the IP header) and provided with the
frame status word. For example, if extension headers were present, their sums can be
subtracted in software from the checksum to isolate the TCP/UDP datagram checksum, if
required.
44.4.8.6.2 Transmit Processing
For IPv6 transmission the SHIFT16 function is supported to process 32-bit aligned
datagrams.
IPv6 has no IP header checksum; therefore, the IP checksum insertion configuration is
ignored.
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K60 Sub-Family Reference Manual, Rev. 6, Nov 2011
Freescale Semiconductor, Inc.