EP0150258A2
Expired / Lapsed
EP
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Method for propagating unknown digital values in a hardware based complex circuit simulation system
Assignee: Valid Logic Systems Inc
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Filing: 1984-08-13
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Granted: —
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Expires: 2004-08-13
Abstract
Abstract In a circuit system simulation model which may comprise a combination of the physical device to be modeled and means for controlling the physical device at normal operating speeds, a method is provided for propagating a simulated unknown signal value which comprises exciting the simulation model with differing pattern sequences a plurality of times, during each excitation sequence changing at least one input value in the input sequence, comparing the sampled values of each resultant output signal, and setting or recognizing as an unknown value any specific output signal which differs as a result of the change in the input sequence. Modification, repetition, sampling and comparison of patterns may be repeated a number of times. Only a fraction of the possible input patterns need to be presented to indicate the propagation of unknown values.
Inventors
- 👤 Curtis L. Widdoes, Jr.
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-26 02:25
CPC Classifications
G; G06; G06F; G06F11/00; G06F11/22; G06F11/26; G06F11/261; G06F30/00; G06F30/30; G06F30/32; G06F30/33
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
209 words
In an apparatus for simulating operation of a digital circuit system, a method for modeling operation of a complex digital device in said digital circuit system wherein a physical specimen of said complex digital device is employed as an operational reference element, said method comprising the steps of: presenting to at least one input terminal of said complex digital device a first sequence of digital-valued signals; registering a first response responsive to said first sequence at at least one selected output terminal of said complex digital device; presenting to said complex digital device input terminal a second sequence of digital-valued signals under identical conditions to said presenting of said first sequence of digital-valued signals, wherein the value of at least one element in said second sequence differs from the value of the corresponding element in said first sequence in order to represent an unknown input value; registering a second response responsive to said second sequence at said complex digital device output terminal; comparing, sample for sample, values of said first response with values of said second response; and in the event values of said first response differ from values of said second response at said digital device output terminal generating an output signal indicating occurrence of a response difference.
Claim 2
Dependent Claim
209 words
In an apparatus for simulating operation of a digital circuit system, a method for modeling operation of a complex digital device in said digital circuit system wherein a physical specimen of said complex digital device is employed as an operational reference element, said method comprising the steps of: presenting to at least one input terminal of said complex digital device a first sequence of digital-valued signals; registering a first response responsive to said first sequence at at least one selected output terminal of said complex digital device; presenting to said complex digital device input terminal a second sequence of digital-valued signals under identical conditions to said presenting of said first sequence of digital-valued signals, wherein the value of at least one element in said second sequence differs from the value of the corresponding element in said first sequence in order to represent an unknown input value; registering a second response responsive to said second sequence at said complex digital device output terminal; comparing, sample for sample, values of said first response with values of said second response; and in the event values of said first response differ from values of said second response at said digital device output terminal generating an output signal indicating occurrence of a response difference.
Claim 3
Dependent Claim
27 words
The method according to claim 1 wherein said presenting steps occur at a clock rate which differs from a clock rate associated with operating said simulation system.
Claim 4
Dependent Claim
43 words
The method according to claim 1 further including the step of generating a specific predefined output signal having a digital value representation for any sample which produces a response whose values do not differ as between said first sequence and said second sequence.
Claim 5
Dependent Claim
29 words
The method according to claim 1 wherein said response difference indicating output signal is a signal specifying those values of said first response and said second response are unknown.
Claim 6
Dependent Claim
21 words
The method according to claim 1 wherein only a fraction of possible input sequence variations is presented to said input terminal.
Claim 7
Dependent Claim
13 words
The method according to claim 5 wherein the fraction is less than one-half.
Claim 8
Dependent Claim
13 words
The method according to claim 5 wherein at least two sequences are employed.
Claim 9
Dependent Claim
37 words
The method according to claim 4 wherein said response difference indicating output signal is substituted for each element of said response signal where said response difference is identified for use in identifying causes of said response difference.
References Cited (Backward Citations)
No citation records indexed.
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