Margin test methods and circuits

摘要

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.

主权项

1. A receiver comprising:
a data-input terminal to receive a data signal; first and second data samplers coupled to the data-input terminal to sample the data signal with respect to respective first and second references on edges of a data clock signal to produce respective first and second streams of data samples on respective first and second data output terminals; a third data sampler coupled to the data-input terminal to sample the data signal with respect to a third reference on edges of a test clock signal to produce a third stream of data samples on a respective third data output terminal; comparison circuitry coupled to the first, second, and third data output terminals to compare the first and second streams of data samples with the third stream of data samples; and error-capturing logic coupled to the comparison circuitry to assert error signals responsive to mismatches between the third stream of data samples and at least one of the first and second streams of data samples.