Information

Enhanced Three-Speed Ethernet Controllers
MPC8308 PowerQUICC II Pro Processor Reference Manual, Rev. 1
Freescale Semiconductor 16-163
The contents of the Tx FCB are defined in Table 16-146.
Table 16-146. Tx Frame Control Block Description
Bytes Bits Name Description
0–1
0 VLN VLAN control word valid. This bit is ignored when the PTP bit is set. VLAN tag is read from
the DFVLAN register if PTP=1.
0 Ignore VLCTL field.
1 If VLAN tag insertion is enabled for eTSEC, use the VLCTL field as the VLAN control
word.
1 IP Layer 3 header is an IP header.
0 Ignore layer 3 and higher headers.
1 Assume that the layer 3 header is an IPv4 or IPv6 header, and take L3OS field as valid.
2 IP6 IP header is IP version 6. Valid only if IP = 1.
0 IP header version is 4.
1 IP header version is 6.
3 TUP Layer 4 header is a TCP or UDP header.
0 Do not process any layer 4 header.
1 Assume that the layer 4 header is either TCP or UDP (see UDP bit), and offload
checksumming on the basis that the IP header has no extension headers.
4 UDP UDP protocol at layer 4.
0 Layer 4 protocol is either TCP (if TUP = 1) or undefined.
1 Layer 4 protocol is UDP if TUP = 1.
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.