Instrument with interface for synchronization in automatic test equipment
First Claim
1. An instrument for an automatic test system in which a communication link carries messages, comprising:
- a) an interface comprising;
i) a reference clock input;
ii) a port to connect to the communication link;
b) a clock generator, the clock generator coupled to the reference clock input and receiving a reference clock from the reference clock input and outputting a local clock;
c) a timing circuit, clocked by the local clock, 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 having an input coupled to the port and an output coupled to the input of the timing circuit.
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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.
34 Citations
17 Claims
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1. An instrument for an automatic test system in which a communication link carries messages, comprising:
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a) an interface comprising;
i) a reference clock input;
ii) a port to connect to the communication link;
b) a clock generator, the clock generator coupled to the reference clock input and receiving a reference clock from the reference clock input and outputting a local clock;
c) a timing circuit, clocked by the local clock, 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 having an input coupled to the port and an output coupled to the input of the timing circuit. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. An integrated circuit comprising an interface adapted for use in an instrument for automatic test equipment having functional circuitry that executes a function in response to a command, comprising
a) a reference clock input; -
b) a communication link input;
c) a command output;
d) a clock generator, the clock generator coupled to the reference clock input and outputting a local clock;
e) a timing circuit, clocked by the local clock, having an input to receive a value representative of a time and an output coupled to the command output, the timing circuit asserting the output at a time represented by a value applied to the input of the timing circuit; and
f) a message processing circuit having an input coupled to the communication link input and an output coupled to the input of the timing circuit. - View Dependent Claims (12, 15, 16, 17)
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- 13. The integrated circuit of claim 111 wherein the timing circuit comprises a counter counting pulses of the local clock.
Specification