US 2014/0153588 A1 · METHODS AND APPARATUS FOR PRECISION TIME STAMPING

Abstract

In a network device, apparatus and methods perform precision time stamping. A time agent receives a master pace signal corresponding to a time representation based on a master real time clock in a master clock domain. A time accumulator accumulates time units one fill quantum at a time based on the master pace signal. The time accumulator decreases the accumulated time units by a leak quantum according to a local clock signal running at a higher frequency than the master pace signal. Correction logic periodically generates, at a granularity corresponding to the frequency of the local clock signal, an updated time representation in a target clock domain based on a residual number of time units in the time accumulator before depositing an additional fill quantum of time units in the time accumulator.

Claims15

Dependent claims

An apparatus comprising:

a serializer/deserializer unit;
an adjustment unit coupled to the serializer/deserializer unit and configured to generate a synchronization signal indicative of the cyclic delay variation of the adjustment unit;
a time agent unit generating a time representation;
a time stamp unit coupled to the adjustment unit and to the time agent unit and configured to receive the synchronization signal and calculate an offset between (i) a time representation received concurrently with the detection of an SOP indicator and (ii) a time representation corresponding to a time at which a specific bit in a packet associated with a time stamp is transmitted or received in a serial bit stream.

1 more element

A method of determining an adjusted time representation in a network device, the method comprising:

receiving at a time stamp unit a time representation for a data packet including a start-of-packet (SOP) indicator;
receiving at the time stamp unit a synchronization signal generated at an adjustment unit;
calculating, according to at least the synchronization signal, an offset between the time indicated by the time representation and a time at which a specific bit in the packet associated with time stamping was received as serial data at a serializer/deserializer unit;
generating the adjusted time representation according to the calculated offset;
and
associating with, appending to, processing, or inserting into the data packet time stamp data indicating the adjusted time representation.

3 more elements

Dependencies are inferred from the claim text.

Methods and apparatus for precision time stamping

Life of this patent

Methods and apparatus for precision time stamping

Life of this patent

Abstract

Claims15