Pattern-based loss of signal detector
AssigneeLSI Corporation
InventorsVladimir Sindalovsky, Mohammad S. Mobin, Lane A. Smith
Life of this patent
Estimating the term…
Abstract
In described embodiments, data pattern-based detection of loss of signal (LOS) is employed for a receive path of serializer/deserializer (SerDes) devices. Pattern-based LOS detection allows for detection of data loss over variety of types of connection media, and is generally insensitive to signal attenuation. More specifically, some described embodiments disclose reliable pattern-based detection of LOS across different connection media for incoming receive data when discreet time decision feedback equalization (DFE) is employed.
Claims20
A pattern-based loss of signal (LOS) detector of a serializer-deserializer (SerDes) receiver, the LOS detector comprising:
- an equalizer including a combiner and a feedback loop having a decision feedback equalization (DFE) circuit and a slicers circuit, wherein the summer combines a receive serial signal from a channel with DFE feedback to provide a combined signal for the slicers circuit;
- a lookup table having i) DFE adaptation values, i) a slicer output from the slicers circuit, and iii) a programmable noise threshold, wherein, when a lookup value in the lookup table falls below the programmable noise threshold, the lookup table generates an expected signal at the slicers circuit in absence of the receive serial signal and generates a mask bit along with an expected bit if a DFE level is below an expected noise level;
- a comparator comparing the slicer output with the expected signal;
- and
- a LOS accumulator and counter circuit accumulating the comparison results from the comparator over pre-determined number of receiver characters,
- wherein a pattern based LOS indicator from the LOS accumulator and counter circuit is set if a signal pattern of the slicer output is defined by the DFE feedback from the equalizer.
The LOS detector of claim 15 wherein a magnitude of an added or subtracted value is defined by a digital value of the corresponding DFE tap coefficient and its weight.
A method of detecting loss of signal (LOS) in a circuit, the method comprising the steps of:
- performing signal equalization to a receive serial signal from a channel by an equalizer, wherein the receive serial signal is combined with a decision feedback equalization (DFE) feedback signal from a DFE circuit in the equalizer to provide a combined signal for a slicers circuit in the equalizer;
- feeding a programmable noise threshold, DFE adaptation values, a slicer output from the slicers circuit into a lookup table circuit, wherein, when a lookup in the lookup table falls below the programmable noise threshold, the lookup table calculates an expected signal at the slicers circuit in absence of the receive serial signal and generates a mask bit along with an expected bit if a DFE level is below an expected noise level;
- comparing the slicer output with the expected signal;
- accumulating the comparison results from the comparator over pre-determined number of receiver characters in a LOS accumulator and counter circuit;
- and
- indicating a LOS by setting a pattern based LOS indicator from the LOS accumulator and counter circuit high if a signal pattern of the slicer output is defined by the DFE feedback from the equalizer.
A non-transitory, machine-readable storage medium, having encoded thereon program code, wherein, when the program code is executed by a machine, the machine implements a method for detecting loss of signal (LOS) in a circuit, comprising the steps of:
- performing signal equalization to a receive serial signal from a channel by an equalizer, wherein the receive serial signal is combined with a decision feedback equalization (DFE) feedback signal from a DFE circuit in the equalizer to provide a combined signal for a slicers circuit in the equalizer;
- feeding a programmable noise threshold, DFE adaptation values, a slicer output from the slicers circuit into a lookup table circuit, wherein, when a lookup in the lookup table falls below the programmable noise threshold, the lookup table calculates an expected signal at the slicers circuit in absence of the receive serial signal and generates a mask bit along with an expected bit if a DFE level is below an expected noise level;
- comparing the slicer output with the expected signal;
- accumulating the comparison results from the comparator over pre-determined number of receiver characters in a LOS accumulator and counter circuit;
- and
- indicating a LOS by setting a pattern based LOS indicator from the LOS accumulator and counter circuit high if a signal pattern of the slicer output is defined by the DFE feedback from the equalizer.
Dependencies are inferred from the claim text.