Automatic test system with synchronized instruments
First Claim
1. A test system, comprising:
- a) a reference clock generator providing a reference clock;
b) a first instrument comprising i) a first local clock generator coupled to the reference clock generator and providing a first local clock generated from the reference clock, ii) a first control circuit storing programmed commands for the plurality of instruments, and c) a second instrument comprising i) a second local clock generator coupled to the reference clock generator and providing a second local clock generated from the reference clock;
ii) a second control circuit having an input and an output, the second control circuit asserting the output at a time specified by a time value provided at the input to the second control circuit;
iii) functional circuitry having a control input coupled to the output of the second control circuit, the functional circuitry executing a function in response to a value asserted at its control input; and
d) a network between at least the first instrument and the second instrument, the network carrying a message that includes a time value, wherein the first control circuit is coupled to the network to provide the time value in the message and the second control circuit is coupled to the network to receive the time value at its input.
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Accused Products
Abstract
A test system with multiple instruments. Some instruments act as controller instruments and others act as controlled instruments. Each instrument includes a clock generator that synthesizes one or more local clocks from a reference clock. The reference clock is a relatively low frequency clock that can be inexpensively but accurately generated and distributed to all of the instruments. A communication link between instruments is provided. Timing circuits within instruments that are to exchange time information are synchronized to establish a common time reference. Thereafter, instruments communicate time dependent commands or status messages asynchronously over the communication link by appending to each message a time stamp reflecting a time expressed relative to the common time reference. The test system includes digital instruments that contain pattern generators that send command messages to analog instruments, which need not include pattern generators. The architecture simplifies design of analog instruments and avoids redesign of analog instrument as pattern rates of digital instruments change.
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Citations
31 Claims
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1. A test system, comprising:
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a) a reference clock generator providing a reference clock;
b) a first instrument comprising i) a first local clock generator coupled to the reference clock generator and providing a first local clock generated from the reference clock, ii) a first control circuit storing programmed commands for the plurality of instruments, and c) a second instrument comprising i) a second local clock generator coupled to the reference clock generator and providing a second local clock generated from the reference clock;
ii) a second control circuit having an input and an output, the second control circuit asserting the output at a time specified by a time value provided at the input to the second control circuit;
iii) functional circuitry having a control input coupled to the output of the second control circuit, the functional circuitry executing a function in response to a value asserted at its control input; and
d) a network between at least the first instrument and the second instrument, the network carrying a message that includes a time value, wherein the first control circuit is coupled to the network to provide the time value in the message and the second control circuit is coupled to the network to receive the time value at its input. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A method of operating a test system comprising at least two instruments, the test system further comprising a communication link between the at least two instruments, the method comprising:
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a) establishing a common time reference between timing circuits in the at least two instruments;
b) sequencing on the first instrument through a test pattern defining events in a test, with a portion of the events to be executed by the first instrument and a portion of the events to be executed by the second instrument;
c) communicating from the first instrument to the second instrument over the communication link to specify at least one event to be executed by the second instrument and a time at which the event is to be executed; and
d) waiting until the specified time and executing the specified event with the second instrument. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31)
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Specification