Ieee 1588-2008 Advanced Timestamps - Altera Cyclone V Device Handbook

cv_54017
2013.12.30
The maximum PTP clock frequency is limited by the maximum resolution of the reference time (20 ns
resulting in 50 MHz) and the timing constraints achievable for logic operating on the PTP clock. In addition,
the resolution, or granularity, of the reference time source determines the accuracy of the synchronization.
Therefore, a higher PTP clock frequency gives better system performance.
The minimum PTP clock frequency depends on the time required between two consecutive SFD bytes.
Because the PHY interface clock frequency is fixed by the IEEE 1588 specification, the minimum PTP clock
frequency required for proper operation depends upon the operating mode and operating speed of the
†
MAC.
Table 17-5: Minimum PTP Clock Frequency Example
Mode
100-Mbps full-duplex
operation
1000-Mbps half-duplex
operation
Related Information
IEEE Standards Association website
For more information on the IEEE standards, refer to the IEEE Standards Association website.

IEEE 1588-2008 Advanced Timestamps

In addition to the basic timestamp features mentioned in IEEE 1588-2002 Timestamps, the EMAC supports
the following advanced timestamp features defined in the IEEE 1588-2008 standard.
• Supports the IEEE 1588-2008 (version 2) timestamp format.
• Provides an option to take a timestamp of all frames or only PTP type frames.
• Provides an option to take a timestamp of only event messages.
• Provides an option to take the timestamp based on the clock type: ordinary, boundary, end-to-end, or
peer-to-peer.
(42)
For details about jam patterns, refer to the IEEE Std 802.3 2008 Part 3: Carrier sense multiple access with Collision
Detection (CSMA/CD) Access Method and Physical Layer Specifications, available on the IEEE Standards
Association website, (http://standards.ieee.org).
Ethernet Media Access Controller
Send Feedback
Minimum Gap Between Two SFDs
168 MII clocks
(128 clocks for a 64-byte
frame + 24 clocks of min
IFG + 16
clocks of preamble)
24 GMII clocks
(4 for a jam pattern sent
just after SFD because
of collision
+ 12 IFG + 8
preamble)
(42)
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IEEE 1588-2008 Advanced Timestamps
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Minimum PTP Frequency
(3 * PTP) + (4 * MII)
<= 168 * MII, that is,
~0.5 MHz ((168
– 4) * 40 ns ÷ 3
= 2180 ns period)
3 * PTP + 4 * GMII <=
24 * GMII, that is,
18.75 MHz
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17-17
Altera Corporation