Information

Enhanced Three-Speed Ethernet Controllers
MPC8308 PowerQUICC II Pro Processor Reference Manual, Rev. 1
Freescale Semiconductor 16-141
16.6.3.2 Transmit Path Off-Load and Tx PTP Packet Parsing
TOE functions for transmit are defined by the contents of the Tx FCB. Figure 16-123 describes the
definition for the Tx FCB.
The user instructs the Tx packet to be timestamped via setting bit 15 in the TxFCB to mark a PTP packet.
TxFCB[VLCTL] can be translated as the Tx PTP packet identification number. BD[TOE] has to be set to
enable transmit PTP packet time stamping. TxFCB[PTP] bit takes precedence over TxFCB[VLN] bit. It
disables per packet VLAN tag insertion. On a PTP packet, VLAN tag can be inserted from the DFVLAN
register. A proposed TxFCB update for the PTP packet is shown in Figure 16-128.
The contents of the Tx FCB are defined in Table 16-136.
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Offset + 0 VLN IP IP6 TUP UDP CIP CTU NPH PTP
Offset + 2 L4OS L3OS
Offset + 4 PHCS
Offset + 6 VLCTL
Figure 16-123. Transmit Frame Control Block
Table 16-136. 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.