Abstract:
The invention relates to a method and device for testing a data link. A single-lane or multi-lane bit error tester that transmits one or more PRBS signals through the data link is augmented with a raw bit error buffer for storing bit error information for each detected error event and an error pattern analyzer. Most frequently occurring intra-lane bit error patterns, inter-lane word error patterns, and bit slip patterns are identified and their characteristics are analyzed so as to provide information indicative of root causes of the detected bit errors and bit slips.
Abstract:
Described are methods and circuits for margin testing digital receivers. These methods and circuits prevent margins from collapsing in response to erroneously received data, and can thus be used in receivers that employ historical data to reduce intersymbol interference (ISI). Some embodiments detect receive errors for input data streams of unknown patterns, and can thus be used for in-system margin testing. Such systems can be adapted to dynamically alter system parameters during device operation to maintain adequate margins despite fluctuations in the system noise environment due to e.g. temperature and supply-voltage changes. Also described are methods of plotting and interpreting filtered and unfiltered error data generated by the disclosed methods and circuits. Some embodiments filter error data to facilitate pattern-specific margin testing.
Abstract:
An integrated circuit includes a plurality of receivers, each having a clock and data recovery circuit. A first local clock recovery circuit in a first receiver can be caused to produce a test clock which simulates a condition to be tested, and while a second receiver in the plurality of receivers that includes a second local clock recovery circuit is caused to use the test clock in place of the reference clock while receiving a test data sequence at its input. The clock and data recovery circuits in the receivers can include clock control loops responsive to loop control signals to modify the selected reference clock to generate the local clock in response to selective one of (i) a corresponding data signal for normal operation or during a test, and (ii) a test signal applied to the clock control loop in which case the test clock is produced.
Abstract:
Embodiments of the present disclosure provide a method for predicting bit errors in a communication channel, comprising generating a model representative of the communication channel, formulating enhanced noise at a first noise level that is higher than a second noise level, the second noise level corresponding to a level of noise that the communication channel experiences during a general operation of the communication channel, simulating an operation of the model by injecting the enhanced noise into the model, determining actual bit errors of the model when the model is simulated with the enhanced noise, and estimating a bit error rate (BER) when the model of the communication channel is operated with noise of the second level. Other embodiments are also described and claimed.
Abstract:
Described are methods and circuits for margin testing digital receivers. These methods and circuits prevent margins from collapsing in response to erroneously received data, and can thus be used in receivers that employ historical data to reduce intersymbol interference (ISI). Some embodiments allows feedback timing to be adjusted independent of the sample timing to measure the effects of some forms of phase misalignment and jitter.
Abstract:
Described are methods and circuits for margin testing digital receivers. These methods and circuits prevent margins from collapsing in response to erroneously received data, and can thus be used in receivers that employ historical data to reduce intersymbol interference (ISI). Some embodiments allows feedback timing to be adjusted independent of the sample timing to measure the effects of some forms of phase misalignment and jitter.
Abstract:
Self testing of a data communication system that includes a presettable scrambler and a complementary presettable descrambler is performed by presetting the presettable scrambler to a preset state. A seed payload field is scrambled using the presettable scrambler to generate fields of a test sequence. The fields of the test sequence are transmitted and corresponding received test sequence fields are received. The received test sequence fields are descrambled using the presettable descrambler to generate respective recovered test sequence fields. Differences between the recovered test sequence fields and the seed payload field are then detected as errors. In an embodiment, the seed payload field and the preset state of the presettable scrambler are chosen to generate a test sequence that imposes a known stress, such as a given run length, to the data communication system.
Abstract:
Described are methods and circuits for margin testing receivers equipped with Decision Feedback Equalization (DFE) or other forms of feedback that employ historical data to reduce intersymbol interference (ISI). In one example, a high-speed serial receiver with DFE injects the correct received data (i.e., the nullexpected datanull) into the feedback path irrespective of whether the receiver produces the correct output data. The margins are therefore maintained in the presence of receiver errors, allowing in-system margin tests to probe the margin boundaries without collapsing the margin limits. Some receivers include local expected-data sources that either store or generate expected data for margin tests. Other embodiments derive the expected data from test data applied to the receiver input terminals.
Abstract:
A dummy error addition circuit for adding a dummy error to an orthogonal modulation symbol data, wherein a value based on a specified bit error rate is loaded to count clock signals at a counter (11), a carrier of the counter (11) stores outputs from a PN data generator (21) in a shift register (22), outputs from a PN comparison circuit (3) when stored data agree with count values of the counter (11) are recognized as error pulses, a bit selector (40) randomly selects, on receiving error pulses and based on outputs from a PN data generator (41), bits to which to add errors in an orthogonal modulation data, e.g. a PSK modulation symbol data, at interval based on a bit error rate, and bits selected from the orthogonal modulation data are inverted in a bit inversion circuit (5) for outputting to thereby add errors.
Abstract:
An adaptive digital data unit (600) initiates and successfully completes a remote loop back test. The adaptive digital data unit (600) has a controller (610), a local transmitter (620), a local receiver (640) a timer (622) and a detector (634). When a remote adaptive digital data unit (600) transmits a first data sequence and a second data sequence, the local adaptive digital data unit (600) receives the second data sequence from the remote digital data unit and determines if the second data sequence matches one of two predetermined data sequences. If so, a test successful flag is generated.