Information

Enhanced Three-Speed Ethernet Controllers
MPC8308 PowerQUICC II Pro Processor Reference Manual, Rev. 1
16-142 Freescale Semiconductor
16.6.3.3 Receive Path Off-Load
Upon receive, the Rx FCB returns the status of frame parse and TOE functions applied to the
accompanying frame. Figure 16-124 describes the definition for the Rx FCB.
0–1
5 CIP Checksum IP header enable.
0 Do not generate an IP header checksum.
1 Generate an IPv4 header checksum.
6 CTU Checksum TCP or UDP header enable.
0 Do not generate a TCP or UDP header checksum. RFC 768 advises that UDP packets
not requiring checksum validation should have their checksum field set to zero.
1 Generate a TCP header checksum if IP = 1 and TUP = 1 and UDP = 0.
7 NPH Disable calculation of TCP or UDP pseudo-header checksum. This bit should be set if IP
options need to be consulted in forming the pseudo-header checksum, as eTSEC does not
examine IP options or extension headers for TCP/IP offload on transmit.
0 Calculate TCP or UDP pseudo-header checksum as normal, assuming that the IP header
has no options.
1 Do not calculate a TCP or UDP pseudo-header checksum, but instead use the value in
field PHCS when determining the overall TCP or UDP checksum.
8–14 — Reserved
15 PTP Indication to the transmitter that this is a PTP packet. Enabling PTP disables per packet
VLAN tag insertion. Instead, VLAN tag will be read from the DFVLAN when the PTP field is
true.
0 Do not attempt to capture transmission event time
1 Valid PTP_ID field. When this packet is transmitted, capture the time of transmission.
Must be clear if TMR_CTRL[TE] is clear.
2–3
0–7 L4OS Layer 4 header offset from start of layer 3 header. The layer 4 header starts L4OS octets
after the layer 3 header if it is present. The maximum layer 3 header length supported is thus
255 bytes, which may prevent TCP/IP offload on particularly large IPv6 headers.
8–15 L3OS Layer 3 header offset from start of frame not including the 8 bytes for this FCB. The layer 3
header starts L3OS octets from the start of the frame including any custom preamble header
that may be present. The maximum layer 2 header length supported is thus 255 bytes.
4–5
0–15 PHCS Pseudo-header checksum (16-bit one’s complement sum with carry wraparound, but without
result inversion) for TCP or UDP packets, calculated by software. Valid only if NPH = 1.
6–7
0–15 VLCTL/
PTP_ID
VLAN control word for insertion in the transmitted VLAN tag. Valid only if VLN = 1.Tx PTP
packet identification number. This number will be copied into the Tx PTP packet time stamp
identification field. PTP field takes precedence over VLN field.
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Offset + 0 VLN IP IP6 TUP CIP CTU EIP ETU — PERR —GPFP
Offset + 2 RQ PRO
Offset + 4
Offset + 6 VLCTL
Figure 16-124. Receive Frame Control Block
Table 16-136. Tx Frame Control Block Description (continued)
Bytes Bits Name Description