Low-latency low-uncertainty timer synchronization mechanism across multiple devices
First Claim
1. A method for synchronizing timing in devices coupled to a data communication link, comprising:
- at a first device, receiving a first time value from a second device through the data communication link, the first time value corresponding to a future point in time;
at the first device, receiving a trigger signal from the second device through the data communication link;
loading the first time value into a timer of the first device, at a first-occurring edge in a first clock signal after the trigger signal is received, wherein the first clock signal is used to increment the timer; and
identifying to the second device a phase of the first clock signal at the time the trigger signal is received,wherein the phase of the first clock signal at the time the trigger signal is received is indicative of a phase difference between first clock signal and a second clock signal that is used by the second device.
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Abstract
Systems, methods, and apparatus for synchronizing timing in devices coupled to a data communication link are disclosed. In one example, a first device programs a future system time value in a second device. The first device launches a low-latency trigger signal that causes the future system time value to be loaded into a timer of the second device when a timer of the first device matches the future system time value. The second device measures phase difference between the trigger signal and edges of a clock signal used for timing in the second device. The phase difference is measured using an oversampling clock that provides a desired measurement reliability. The measured phase difference permits the first device to accurately determine system time as applied to the second device. The trigger signal can be provided on existing pins used by first and second devices in accordance with communication protocols and specifications.
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Citations
30 Claims
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1. A method for synchronizing timing in devices coupled to a data communication link, comprising:
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at a first device, receiving a first time value from a second device through the data communication link, the first time value corresponding to a future point in time; at the first device, receiving a trigger signal from the second device through the data communication link; loading the first time value into a timer of the first device, at a first-occurring edge in a first clock signal after the trigger signal is received, wherein the first clock signal is used to increment the timer; and identifying to the second device a phase of the first clock signal at the time the trigger signal is received, wherein the phase of the first clock signal at the time the trigger signal is received is indicative of a phase difference between first clock signal and a second clock signal that is used by the second device. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. An apparatus, comprising:
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a data communication link; a first device coupled to the data communication link and adapted to define system time; and a second device coupled to the data communication link and having a timer adapted to track the system time, wherein the second device is configured to; receive a first time value from the first device through the data communication link, the first time value corresponding to a future point in time; receive a trigger signal from the first device through the data communication link; load the first time value into the timer, at a first-occurring edge in a first clock signal after the trigger signal is received, wherein the first clock signal is used to increment the timer; and identify to the first device a phase of the first clock signal at the time the trigger signal is received, wherein the phase of the first clock signal at the time the trigger signal is received is indicative of a phase difference between first clock signal and a second clock signal that is used by the first device. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19)
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20. A method for synchronizing system time used by devices coupled to a data communication link, comprising:
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determining a first time value that corresponds to a future point in system time at a first device; transmitting a second time value from the first device to a second device through the data communication link, the second time value being incrementally greater than the first time value; transmitting a trigger signal from the first device to the second device through the data communication link when the first time value is determined to match a value output by a system timer operated by the first device, wherein the system timer is clocked using a first clock signal; receiving from the second device an indication of phase of a second clock signal when the trigger signal was received by the second device, wherein the second clock signal is used by the second device to maintain a local timer; and calculating a phase difference between the first clock signal and the second clock signal using the indication of the phase of the second clock signal when the trigger signal was received by the second device. - View Dependent Claims (21, 22, 23, 24, 25)
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26. An apparatus, comprising:
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means for determining a first time value that corresponds to a future point in system time at a first device coupled to a data communication link; means for transmitting a second time value from the first device to a second device through the data communication link, the second time value being incrementally greater than the first time value; means for transmitting a trigger signal from the first device to the second device through the data communication link when the first time value is determined to match a value output by a system timer operated by the first device, wherein the system timer is clocked using a first clock signal; means for receiving from the second device an indication of phase of a second clock signal when the trigger signal was received by the second device, wherein the second clock signal is used by the second device to maintain a local timer; and means for calculating a phase difference between the first clock signal and the second clock signal using the indication of the phase of the second clock signal when the trigger signal was received by the second device. - View Dependent Claims (27, 28, 29, 30)
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Specification