SLAU723A October 2017 – October 2018 MSP432E401Y , MSP432E411Y
In IPv4 datagrams, the integrity of the header fields is indicated by the 16-bit Header Checksum field (the eleventh and twelfth bytes of the IPv4 datagram). The checksum offload engine detects an IPv4 datagram when the Ethernet frame's Type field has the value 0x0800 and the IP datagram's Version field has the value 0x4. The input frame's checksum field is ignored during calculation and replaced with the calculated value. IPv6 headers do not have a checksum field. Therefore, the checksum offload does not modify the IPv6 header fields.
The result of this IP header checksum calculation is indicated by the IP Header Error status bit in the Transmit status (Bit 16 in TDES0). This status bit is set whenever the values of the Ethernet Type field and the IP header's Version field are not consistent, or when the Ethernet frame does not have enough data, as indicated by the IP header Length field. In other words, this bit is set when an IP header error is asserted under the following circumstances:
If the checksum offload engine detects an IP header error, it still inserts an IPv4 header checksum if the Ethernet Type field indicates an IPv4 payload.