Receive Time Stamp and Sequence ID Registers
BCM5718 Programmer’s Guide
Broadcom
®
January 29, 2016 • 5718-PG108-R
Page 158
Receive Time Stamp and Sequence ID Registers
The time of reception of chosen PTP frames shall be recorded by hardware in the RX Time Stamp Register. The
place of time capture is the GMII interface, the point of capture is arrival of the SOF octet and the reference of
time is the EAV Reference Count. Thus, the time of appearance of the SOF octet of every RX frame on the
internal GMII interface needs to be recorded by hardware and held it in a temporary register or a temporary
FIFO. After reception of a complete frame, upon examining the RX Frame cracker results, hardware shall decide
if that particular Frame had the Host SW desirable PTP message type and only then it will transfer its acquired
time stamp into the RX Time Stamp Register. Along with the RX Time Stamp, hardware shall also capture the
respective PTP packets sequenceID field. Hardware shall also mark a status field in a packet's Receive BD
indicating if the packet was a PTP packet and also if RX Time Stamp was captured for the packet.
Table 46: Receive Return Ring RBD Flags
Bit # Flag Name
Flag Description
1:0
PTP Packet Type
00: PTP Delay Request Packet
01: PTP Delay Response Packet
10: PTP Sync Packet
11: All other type of PTP Packets
2
BD_FLAG_END
The frame ends at the end of the data in this buffer descriptor.
3
RSS_HASH_VALID
If this bit is 1, then the RSS_HASH_TYPE field is valid. Else the
RSS_HASH_TYPE field is meaningless and must be ignored for
this frame.