Synchronization module
A synchronization module for providing synchronization messages to be sent with a time stamp in accordance with the PTP protocol of standard IEEE 1588 is provided. The synchronization module comprises a program module for generating a synchronization message to be sent and for providing the synchronization message with a first time stamp, and a hardware-implemented time stamp module which receives synchronization messages from the program module and forwards them in accordance with the PTP protocol. The time stamp module comprises a real time clock, a message detector for recognizing a synchronization message by its difference in relation to other messages and a message manipulator for overwriting the first time stamp in a synchronization message recognized by the message detector with a second time stamp actually retrieved from the real time clock.
1. A synchronization module for providing synchronization messages required to be sent with a timestamp according to the Precision Time Protocol of the IEEE 1588 standard, comprising:
a program module that generates a synchronization message to be sent and provides the synchronization message with a first timestamp according to the Precision Time Protocol; and
a hardware timestamp module that accepts synchronization messages from the program module and sends synchronization messages according to the Precision Time Protocol, comprising:
a realtime clock,
a message detector that recognizes a synchronization message,
a message timestamp point store configured to store a second timestamp called up from the realtime clock for a recognized synchronization message, the second timestamp being stored when the message timestamp point store receives a corresponding trigger signal from a module of a physical interface that is generated when a preamble of the synchronization message is recognized; and
a message manipulator that overwrites the first timestamp in the recognized synchronization message with the second timestamp.
2. The synchronization module as claimed in claim 1 , wherein the message detector and message manipulator are coupled directly to the realtime clock.
3. The synchronization module as claimed in claim 1 , further comprising a buffer coupled to the message detector that buffers synchronizing information.
4. The synchronization module as claimed in claim 1 , wherein the message manipulator enters a receive timestamp from the realtime clock into an additional field of a received synchronization message.
5. The synchronization module as claimed in claim 1 , wherein the message manipulator determines a current checksum for the synchronization message provided with the second timestamp and overwrites the checksum with a new checksum.
6. The synchronization module as claimed in claim 5 , wherein the message detector and message manipulator are coupled directly to the realtime clock.
7. The synchronization module as claimed in claim 6 , further comprising a buffer coupled to the message detector that buffers synchronizing information.
8. The synchronization module as claimed in claim 7 , wherein the message manipulator is also configured to enter a receive timestamp from the realtime clock into an additional field of a received synchronization message.
9. The synchronization module of claim 1 wherein the message detector and message manipulator have direct hardware access to the realtime clock and wherein the second timestamp being stored when the message timestamp point store receives a corresponding trigger signal from the module of a physical interface that is generated when the preamble of the synchronization message is recognized such that a jitter caused by the module of the physical interface is at least partially avoidable.
10. The synchronization module of claim 1 further comprising a phase-locked loop connected to the realtime clock, the realtime clock being adjustable by regulating the phase-locked loop.
11. The synchronization module of claim 1 wherein the physical interface is clocked using a clock signal that is also used for the hardware timestamp module.
12. The synchronization module of claim 1 wherein the synchronization module is employed as an Application Specific Integrated Circuit, a Field Programmable Gate Array, or a Complex Programmable Logic Device.