On-chip eye viewer architecture for highspeed transceivers

• US 8,744,012 B1
• Filed: 02/08/2012
• Issued: 06/03/2014
• Est. Priority Date: 02/08/2012
• Status: Expired due to Fees

• Current Assignee: Altera Corporation (Intel Corporation)
• Original Assignee: Altera Corporation (Intel Corporation)
• Inventors: Ding, Weiqi, Pan, Mingde, Shumarayev, Sergey, Li, Peng
• Primary Examiner(s): Joseph, Jaison
• Application Number:
  US13/369,108
• Time in Patent Office: 846 Days
• Field of Search: 375/371, 375/228, 375/295, 375/317, 375/355
• US Class Current: 375/316
• CPC Class Codes: G01R 31/31711 Evaluation methods, e.g. shmoo plots
• CPC Class Codes: H04L 1/203 Details of error rate determination, e.g. BER, FER or WER

Abstract

System, methods, and devices for determining an eye diagram of a serial input signal to an integrated circuit without an oscilloscope are provided. For example, one embodiment of an integrated circuit device may be capable of determining an eye diagram associated with a serial input signal either during or after equalization. The device may include an equalizer and eye viewer circuitry configured to select a node of the equalizer for eye monitoring of the input signal, which may be during or after equalization. In one embodiment, the eye viewer circuitry may provide a separate sampler for each respective node, while sharing a control logic and phase interpolator among the samplers. The eye viewer circuitry may determine horizontal and vertical boundaries of the eye diagram associated with the serial input signal, as seen from the selected node of the equalizer.

Claims

1. A method of manufacturing an integrated circuit (IC) device comprising:

providing an equalizer of the IC device, wherein the equalizer comprises a plurality of internal nodes, each of the internal nodes being at an output of a respective stage of equalization in the equalizer, wherein each of the internal nodes is selectable for analysis of a serial input signal propagated through the equalizer; and

providing eye viewer circuitry of the IC device to analyze a serial signal from a selected internal node to determine coordinates useful for generating a corresponding eye diagram of the serial signal.

2. The method of claim 1, comprising configuring the eye viewer circuitry to determine horizontal and vertical boundaries of the eye diagram by sampling the serial signal at variable phase offsets from a clock signal associated with the serial input signal and at variable reference voltages, and testing error rates associated with the sampled signal.

3. The method of claim 2, comprising configuring the eye viewer circuitry to test the error rates associated with the sampled signal by determining at least one of a bit error rate (BER) or a cyclic redundancy check (CRC) error rate, or a combination thereof.

4. The method of claim 2, comprising configuring the eye viewer circuitry to:

determine the variable phase offsets by providing a first control signal indicating a phase offset from control logic of the eye viewer circuitry to a phase interpolator, and to determine the variable reference voltages by providing a second control signal indicating a reference voltage from the control logic to a sampler configured to sample the serial signal.

5. The method of claim 4, comprising configuring the phase interpolator to receive the clock signal associated with the serial input signal and provide an offset clock signal to the sampler based at least partially upon the first control signal.

6. The method of claim 1, comprising providing control logic to enable the selection of one of the internal nodes for analysis by enabling a selection signal provided to a multiplexer to cause the multiplexer to output a sampled signal corresponding to the serial signal at the selected internal node being analyzed by the eye viewer circuitry signal.

7. The method of claim 1, comprising enabling the serial input signal to operate at approximately 28 Gbps or higher.

8. An integrated circuit (IC) device comprising:

a receiver;

an equalizer configured to equalize a serial input signal received by the receiver, wherein the equalizer comprises a plurality of equalizer stages, wherein the output of each equalizer stage comprises an internal node of the equalizer, and the equalizer is configured such that each of the internal nodes is selectable for analysis of a serial signal at the internal node;

a clock and data recovery circuit configured to receive an output of the equalizer and output a recovered data signal and a recovered clock signal;

eye viewer circuitry configured to select one of the internal nodes of the equalizer for analysis of a serial signal at the selected internal node and to determine an eye diagram corresponding to the serial signal from the selected internal node; and

a deserializer configured to output a first parallel signal based upon the recovered data signal and the recovered clock signal from the clock and data recovery circuit when the IC device is operating in a normal traffic mode and to output a second parallel signal based upon a selected offset data signal and an offset clock signal from the eye viewer circuitry when the IC device is operating in an eye viewer mode, wherein the selected offset data signal is determined by sampling the serial signal from the selected internal node.

9. The IC device of claim 8, wherein the eye viewer circuitry comprises:

a plurality of samplers, wherein each sampler is configured to receive a serial signal from a respective one of the internal nodes, a reference voltage, and the offset clock signal, and to output an offset data signal based at least partially upon the received serial signal, the reference voltage, and the offset clock signal;

control logic configured to provide a reference voltage to each of the samplers and a first control signal indicative of a phase offset;

a phase interpolator configured to receive the recovered clock signal and to output the offset clock signal based at least partially upon the first control signal to each of the samplers;

error checking circuitry configured to detect an error rate of data contained in the selected offset data signal to produce an error rate signal; and

a selection circuit configured to receive the respective offset data signal from each of the samplers and to output one of the offset data signals as the selected offset data signal in response to a first selection signal provided by the control logic.

10. The IC device of claim 9, wherein the control logic is configured to receive the error rate signal, vary the first control signal to vary the phase offset, and vary the reference voltage to determine the eye diagram associated with the serial signal from the selected internal node based at least partially upon the error rate indicated by the error rate signal.

11. The IC device of claim 8, wherein the equalizer comprises a short-reach equalizer stage, a long-reach equalizer stage, and a decision feedback equalizer stage, and wherein the internal nodes comprise a first internal node representative of the output of the short-reach equalizer stage, a second internal node representative of the output of the long-reach equalizer, and a third internal node representative of the output of the decision feedback equalizer.

12. The IC device of claim 9, wherein the control logic and the phase interpolator of the eye viewer circuitry are shared between each of the samplers.

13. The IC device of claim 9, comprising a sampler configured to receive a serial output signal from an internal node of a transmitter of the IC device, and wherein the eye viewer circuitry is configured to analyze the serial output signal and to determine an eye diagram corresponding to the serial output signal if the internal node of the transmitter is selected.

14. The IC device of claim 8, comprising:

a first multiplexer configured to receive the recovered data signal from the clock and data recovery circuit as a first input and the selected offset data signal from the eye viewer circuitry as a second input; and

a second multiplexer configured to receive the recovered clock signal from the clock and data recovery circuit as a first input and the offset clock signal from the eye viewer circuitry as a second input;

wherein the first and second multiplexers are responsive to a common control signal, and wherein the first and second multiplexers are configured to select the recovered data signal and recovered clock signal, respectively, if the common control signal indicates a first binary value, and to select the offset data signal and offset clock signal, respectively, if the common control signal indicates a second binary value.

15. The IC device of claim 9, wherein the control logic is configured to determine horizontal boundaries of the eye diagram by increasing or decreasing the phase offset indicated by the first control signal until the error rate exceeds a threshold, and to determine the vertical boundaries of the eye diagram by increasing or decreasing the reference voltage until the error rate exceeds the threshold.

16. The IC device of claim 9, wherein each of the samplers comprises a threshold voltage comparator configured to output a first binary value if its respective serial signal exceeds the reference voltage and a second binary value if its respective serial signal is less than the reference voltage.

17. The IC device of claim 9, wherein the reference voltage is determined using a digital to analog converter (DAC).

18. The IC device of claim 8, wherein the serial input signal has a data rate of at least 28 Gbps.

19. An integrated circuit (IC) device comprising:

a receiver comprising an equalizer configured to equalize a received serial input signal;

a clock and data recovery (CDR) circuit configured to receive the equalized serial input signal and to output a recovered data signal and a recovered clock signal;

eye viewer circuitry configured to receive a serial signal from the IC device for analysis, to output an offset data signal and an offset clock signal, and to determine an eye diagram of the serial signal when the IC device is operating in an eye viewer mode;

a first deserializer configured output a first parallel signal based upon the recovered data signal and the recovered clock signal from the CDR circuit when the IC device is operating in either of a normal mode or an uninterrupted eye viewer mode, and to output the first parallel signal based upon the offset data signal and the offset clock signal from the eye viewer circuitry if the IC device is operating in an interrupted eye viewer mode, wherein the second parallel signal is provided to an error checking circuitry for determination of an error rate signal; and

a second deserializer configured to output a second parallel signal based upon the offset data signal and the offset clock signal when the IC is operating in the uninterrupted eye viewer mode, wherein the third parallel signal is provided to the error checking circuit for determination of the error rate signal.

20. The IC device of claim 19, comprising:

a first multiplexer configured to receive the recovered data signal from the CDR circuit as a first input and the offset data signal from the eye viewer circuitry as a second input; and

a second multiplexer configured to receive the recovered clock signal from the CDR circuit as a first input and the offset clock signal from the eye viewer circuitry as a second input;

wherein, when the IC device is operating in either the normal mode or the uninterrupted eye viewer mode, the first and second multiplexers are configured to pass the recovered data signal and the recovered clock signal, respectively, and wherein, when the IC device is operating in the interrupted eye viewer mode, the first and second multiplexers are configured to pass the offset data signal and the offset clock signal, respectively.

21. The IC device of claim 20, comprising:

a third multiplexer configured to receive the first parallel signal from the first deserializer as a first input and the second parallel signal from the second deserializer as a second input, wherein the third multiplexer is configured to pass the first parallel signal to the error checking circuitry if the IC device is operating in either of the normal mode or the interrupted eye viewer mode and to pass the second parallel signal to the error checking circuitry if the IC device is operating in the uninterrupted eye viewer mode.

22. The IC device of claim 19, wherein the uninterrupted eye viewer mode allows for the determination of the eye diagram corresponding to the serial signal received by the eye viewer circuitry without interrupting normal traffic comprising the recovered data signal through the IC device.

23. The IC device of claim 19, wherein the eye viewer circuitry is configured to select the received serial signal from a plurality of serial signals comprising the output of the equalizer, a serial signal from an internal node within the equalizer, or a serial signal from a transmitter of the IC device.

24. The IC device of claim 19, wherein the IC device comprises a field-programmable gate array.

25. A method comprising:

receiving a serial input signal at a receiver of an integrated circuit (IC) device;

equalizing the serial input signal using a equalizer comprising a plurality of equalizer stages to produce an equalized signal;

selecting a serial signal from the output of one of equalizer stages for analysis;

sampling the selected serial signal at variable phase offsets from a clock signal associated with the equalized signal and at variable threshold voltages using a sampler associated with the selected serial signal;

detecting an error rate in the sampled signal using error checking circuitry;

determining an error rate signal based on the detected error rate; and

determining one or more coordinates useful for generating an eye diagram of the selected serial signal based at least in part on the error rate signal using circuitry configured to vary the phase offsets and the threshold voltages.

26. The method of claim 25, comprising using clock and data recovery circuitry to recover the clock signal associated with the equalized signal.

27. The method of claim 25, comprising, in response to the eye diagram, receiving a request to modify one or more parameters of the equalizer to cause the eye diagram to become more open and modifying the one or more parameters.

28. The method of claim 25, wherein the varying of the phase offsets determines the horizontal boundaries of the eye diagram and wherein the varying of the threshold voltages determines the vertical boundaries of the eye diagram.

29. The method of claim 25, wherein selecting the serial signal comprises, selecting the serial signal from the output of one of the equalizer stages or, additionally, from a serial signal transmitted by a transmitter of the IC device.