National Instruments Corporation

Adam C Ullrich

Sundeep Chandhoke

Kunal H Patel

Rodney D Greenstreet

Kalyanramu Vemishetty

Lee E Mohrmann

Stephen A Hanssen

System and method for synchronizing devices. A device reads a first counter coupled to and associated with a master clock and a second counter coupled to and associated with the device, where the device is one of one or more devices coupled to the master clock and each other via a switched fabric, where each device includes a respective clock, and is coupled to and associated with a respective second counter. Each of the first counter and the second counters is accessible by each of the one or more devices. The device determines a difference between the device's associated second counter and the first counter, and determines and stores a time reference for the device relative to the master clock based on the determined difference, where the time reference is useable to timestamp events or synchronize future events.

Clock distribution in a distributed system with multiple clock domains over a switched fabric

A system may include a plurality of subsystems, e.g. instrumentation units housed in separate chassis, each chassis including multiple instrumentation devices, e.g. data acquisition cards. Each subsystem may generate a local reference clock, which may be phase aligned and locked with respect to one or more similar reference clocks of other subsystems, via a high-level precision time protocol (PTP). Each instrumentation device within a given subsystem may generate its own sample clock based on the local reference clock, and may generate its own trigger clock based on its own sample clock. All trigger clocks may be synchronized with respect to each other through a future time event issued using the PTP, and each instrumentation device may then use its trigger clock to synchronize any received trigger pulses, which may also be issued through future time events using the PTP. This results in synchronizing the received triggers across all participating instrumentation devices across all participating subsystems, ensuring that data acquisition is properly synchronized across the multiple subsystems.

Cross controller clock synchronization

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Adam C Ullrich