Table 20-13. Enhanced Received Descriptor 4 (RDES4) (continued)
Description
Bit
Timestamp Dropped
When set, this bit indicates that the timestamp was captured for this frame but got dropped in the RX FIFO
because of overflow.
14
PTP Version
When set, this bit indicates that the received PTP message uses the IEEE 1588 version 2 format. When reset,
it uses the version 1 format.
13
PTP Frame Type
When set, this bit indicates that the PTP message is sent directly over Ethernet. When this bit is clear and the
message type is non-zero, it indicates that the PTP message is sent over UDP-IPv4 or UDP-IPv6. The information
about IPv4 or IPv6 can be obtained from Bits 6 and 7.
12
MessageType
These bits are encoded to give the type of the message received:
■
0x0= No PTP message received
■
0x1= SYNC (all clock types)
■
0x2= Follow_Up (all clock types)
■
0x3= Delay_Req (all clock types)
■
0x4= Delay_Resp (all clock types)
■
0x5= Pdelay_Req (in peer-to-peer transparent clock)
■
0x6= Pdelay_Resp (in peer-to-peer transparent clock)
■
0x7= Pdelay_Resp_Follow_Up (in peer-to-peer transparent clock)
■
0x8= Announce
■
0x9= Management
■
0xA= Signaling
■
0xB to 0xE= Reserved
■
0xF= PTP packet with Reserved message type
11:8
IPv6 Packet Received
When set, this bit indicates that the received packet is an IPv6 packet. This bit is updated only when the
IPC
bit of the
EMACCFG
register is set.
7
IPv4 Packet Received
When set, this bit indicates that the received packet is an IPv4 packet. This bit is updated only when the
IPC
bit of the
EMACCFG
register is set.
6
IP Checksum Bypassed
When set, this bit indicates that the checksum offload engine is bypassed.
5
IP Payload Error
When set, this bit indicates that the 16-bit IP payload checksum (that is, the TCP, UDP, or ICMP checksum)
that the core calculated does not match the corresponding checksum field in the received segment. It is also
set when the TCP, UDP, or ICMP segment length does not match the payload length value in the IP Header
field. This bit is valid when either Bit 7 or Bit 6 is set.
4
IP Header Error
When set, this bit indicates that either the 16-bit IPv4 header checksum calculated by the core does not match
the received checksum bytes, or the IP datagram version is not consistent with the Ethernet Type value. This
bit is valid when either Bit 7 or Bit 6 is set.
3
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TM4C1294NCPDT Microcontroller