Intel® Agilex™ Hard Processor System Technical Reference Manual

ID 683567
Date 2/14/2023
Public

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17.6.3.2.4. Receive Descriptor Field 4 (RDES4)

The extended status is written only when there is status related to IPC or timestamp available. The availability of extended status is indicated by Bit 0 in RDES0. This status is available only when the Advance Timestamp or IPC Full Offload feature is selected. 
Table 180.  Receive Descriptor Field 4 (RDES4)

Bit

Description

31:28

Reserved 

27:26

Layer 3 and Layer 4 Filter Number Matched

These bits indicate the number of the Layer 3 and Layer 4 Filter that matched the received frame.

  • 00: Filter 0
  • 01: Filter 1
  • 10: Filter 2
  • 11: Filter 3

This field is valid only when Bit 24 or Bit 25 is set. When more than one filter matches, these bits give only the lowest filter number. 

25

Layer 4 Filter Match

When set, this bit indicates that the received frame matches one of the enabled Layer 4 Port Number fields. This status is given only when one of the following conditions is true:

  • Layer 3 fields are not enabled and all enabled Layer 4 fields match.
  • All enabled Layer 3 and Layer 4 filter fields match.

When more than one filter matches, this bit gives the layer 4 filter status of filter indicated by Bits [27:26]. 

24

Layer 3 Filter Match

When set, this bit indicates that the received frame matches one of the enabled Layer 3 IP Address fields.

This status is given only when one of the following conditions is true:

  • All enabled Layer 3 fields match and all enabled Layer 4 fields are bypassed.
  • All enabled filter fields match.

When more than one filter matches, this bit gives the layer 3 filter status of the filter indicated by Bits [27:26]. 

23:15

Reserved

14

Timestamp Dropped

When set, this bit indicates that the timestamp was captured for this frame but got dropped in the MTL RX FIFO buffer because of overflow.

13

PTP Version

When set, this bit indicates that the received PTP message has the IEEE 1588 version 2 format. When clear, it has the version 1 format.

12

PTP Frame Type

When set, this bit indicates that the PTP message is sent directly over Ethernet. When this bit is not set 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.

11:8

Message Type

These bits are encoded to give the type of the message received.

  • 0000: No PTP message received
  • 0001: SYNC (all clock types)
  • 0010: Follow_Up (all clock types)
  • 0011: Delay_Req (all clock types)
  • 0100: Delay_Resp (all clock types)
  • 0101: Pdelay_Req (in peer‑to‑peer transparent clock)
  • 0110: Pdelay_Resp (in peer‑to‑peer transparent clock)
  • 0111: Pdelay_Resp_Follow_Up (in peer‑to‑peer transparent clock)
  • 1000: Announce
  • 1001: Management
  • 1010: Signaling
  • 1011‑1110: Reserved
  • 1111: PTP packet with Reserved message type

7

IPv6 Packet Received

When set, this bit indicates that the received packet is an IPv6 packet. This bit is updated only when Bit 10 (IPC) of Register 0 (MAC Configuration Register) is set.

6

IPv4 Packet Received

When set, this bit indicates that the received packet is an IPv4 packet. This bit is updated only when Bit 10 (IPC) of Register 0 (MAC Configuration Register) is set.

5

IP Checksum Bypassed

When set, this bit indicates that the checksum offload engine is bypassed.

4

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 EMAC 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.

3

IP Header Error

When set, this bit indicates that either the 16‑bit IPv4 header checksum calculated by the EMAC 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.

2:0

IP Payload Type

These bits indicate the type of payload encapsulated in the IP datagram processed by the receive Checksum Offload Engine (COE). The COE also sets these bits to 0 if it does not process the IP datagram’s payload due to an IP header error or fragmented IP.

  • 0x0: Unknown or did not process IP payload
  • 0x1: UDP
  • 0x2: TCP
  • 0x3: ICMP
  • 0x4–0x7: Reserved

This bit is valid when either Bit 7 or Bit 6 is set.