Download IEEE 1588 Implementation on a ColdFire Processor

IEEE 1588 Basic Overview
System A
(Master)
t3
System B
(Slave)
_requ
delay
msg
t2
t2 = timestamp
of delay_req msg sent
delay_
re
(includ sp msg
es t3)
t3 = timestamp
of delay_req msg received
Equation 2:
t3 – t2 = delay - offset
Figure 2. Offset and Delay Measurement — Delay Messages
Figure 3 serves as an example of the IEEE 1588 synchronization message sequence.
100
102
104
Master Clock
PTP Appl.
G/MII
t0
Estimated
Send Time
(100)
Precise
Send
Time
(101)
Slave Clock
G/MII
PTP Appl.
104
SYNC(100??
)
t1
FOLLOW_U
P(101!)
106
t3
B
DELAY_REQ
t2
108
110
112
Precise
Receive
Time
(108)
DELAY_RES
P(108)
Key Equations:
Example:
A = t1 – t0 = Delay + Offset
A = 106 – 101 = 5
B = t3 - t2 = Delay – Offset
B = 108 – 111 = -3
Delay = (A+B) / 2
Delay = (5-3) / 2 = 1
Offset = (A-B) / 2
Offset = (5+3) / 2 = 4
A
106
Precise
Receive
Time (106)
108
Offset
Computation
110
Precise
Send Time
(111)
112
114
116
UDP port 319: Sync and
Delay_Req
UDP port 320: Follow_up,
Delay_Resp, and Mgmt
Figure 3. IEEE 1588 Synchronization Message Sequence
For more information about the IEEE 1588 standard, visit the web page for the National Institute of
Standards and Technology.
IEEE 1588 Implementation on a ColdFire Processor, Rev. 0
4
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