Patent ID: 7769559

Claim:
An apparatus for controlling timing of events in an instrument for an automatic test system, the instrument being of the type comprising: a) an interface comprising: i) a reference clock input adapted to receive a reference clock with a resolution; and ii) a port to connect to a communication link that carries messages b) a clock generator coupled to the reference clock input and adapted to receive a reference clock from the reference clock input and to output a local clock having a higher resolution than the resolution of the reference clock; c) a timing circuit, tracking time based on the local clock, the timing circuit having an input to receive a value representative of a time and an output, the timing circuit asserting the output at a time represented by the value received at the input; and d) a message processing circuit comprising: i) an input coupled to the port of the interface; ii) an output coupled to the clock generator, the value of the output derived from a message received over the communication link and specifying a time relative to the reference clock to align the local clock to a second local clock in a device and a value used in synchronizing time tracked in the timing circuit to time tracked in the device; and iii) an output coupled to the input of the timing circuit, the value of the output derived from a message received over the communication link and specifying a time of an event relative to time tracked based on the second local clock in the device, the time of the event specified with a resolution greater than the resolution of the reference clock.