摘要:
Techniques are disclosed for asynchronous calibration for eye diagram generation. For example, a method for calibrating a process for generating a data eye associated with a received signal comprises the following steps. Samples of the received signal are obtained for a first unit interval using a first data latch and a roaming latch. A delay offset is determined between the first data latch and the roaming latch by comparing at least one sample obtained using the first data latch and at least one sample obtained using the roaming latch, wherein the delay offset determined by the comparison is used to calibrate the process for generating the data eye associated with the received signal. A similar comparison may be done for a second data latch and used to calibrate the process. The method is able to find the accurate position of each data latch with respect to the roaming latch so as to improve the accuracy of data decoding in a digital receiver, i.e., provide receiver optimization.
摘要:
Techniques are disclosed for asynchronous calibration for eye diagram generation. For example, a method for calibrating a process for generating a data eye associated with a received signal comprises the following steps. Samples of the received signal are obtained for a first unit interval using a first data latch and a roaming latch. A delay offset is determined between the first data latch and the roaming latch by comparing at least one sample obtained using the first data latch and at least one sample obtained using the roaming latch, wherein the delay offset determined by the comparison is used to calibrate the process for generating the data eye associated with the received signal. A similar comparison may be done for a second data latch and used to calibrate the process. The method is able to find the accurate position of each data latch with respect to the roaming latch so as to improve the accuracy of data decoding in a digital receiver, i.e., provide receiver optimization.
摘要:
A frequency-lock detector (FLD) adapted to register more than one target count per period of a target clock signal to generate a count value related to a frequency difference between the target clock signal and a reference clock signal. In various embodiments of the invention, this count registration is implemented by multiplying the target clock signal, discerning two or more phases of a signal, and/or organizing a count pipeline. In a representative embodiment, an FLD of the invention has a counter circuit and a control circuit. The counter circuit has (i) a frequency multiplier adapted to multiply the frequency of the target clock signal to generate a multiplied signal, (ii) two target counters adapted to register counts based on occurrences of two different phases of the accelerated signal to generate two auxiliary numbers, and (iii) a multiplexer adapted to select an appropriate one of the auxiliary numbers as the count value related to the frequency difference. The control circuit has a reference counter adapted to control, based on the reference clock signal, the count registration in the target counters and the value selection in the multiplexer.
摘要:
Methods and apparatus are provided for detecting and decoding adaptive equalization training frames (having a frame marker comprised of a string of binary ones and binary zeroes). Training frames are detected by shifting the received data; inserting at least one binary value at one end of the shifted received data to generate a modified version of the received data; applying a logic function to the received data and the modified version of the received data that identifies when corresponding bit positions have different values; and detecting the frame marker when an output of the logic function has a first binary value in an approximate middle of a string of a second binary value. The training frames are decoded using a distance between the approximate center of the frame maker and a predefined binary value in an output of the logic function.
摘要:
Methods and apparatus are provided for detecting and decoding adaptive equalization training frames (having a frame marker comprised of a string of binary ones and binary zeroes). Training frames are detected by shifting the received data; inserting at least one binary value at one end of the shifted received data to generate a modified version of the received data; applying a logic function to the received data and the modified version of the received data that identifies when corresponding bit positions have different values; and detecting the frame marker when an output of the logic function has a first binary value in an approximate middle of a string of a second binary value. The training frames are decoded using a distance between the approximate center of the frame maker and a predefined binary value in an output of the logic function.
摘要:
Communications equipment can be tested using a test pattern encapsulated within a frame, and offsetting the test pattern in each successive frame. In equipment having a number of data latches receiving serial input, the introduction of the offset allows each latch, over time, to be exposed to the same pattern as the other latches. That is, the latches “see” different portions of the pattern at a given time, but over time, each can be exposed to the full pattern. Otherwise, each latch would “see” its own static pattern, different from the other latches, but the same over time with respect to itself. The offset can enhance diagnostic capabilities of the test pattern.
摘要:
Communications equipment can be tested using a test pattern that is modified compared to, and more exploitive than, a standard test pattern. Test patterns can be employed that have lengthened or shortened consecutive identical digit (CID) portions, or that have lengthened or shortened pseudo random bit sequence (PRBS) portions. In some cases, PRBS polynomials are not re-seeded after each CID. Further, different order polynomials can be employed for different applications. Exemplary applications can include test equipment and built-in self-test capability for integrated circuits.
摘要:
Methods and apparatus are provided for improving the jitter tolerance in an SFP limit amplified signal. Jitter tolerance is improved in a communications receiver by applying a received signal to an SFP limiting amplifier; and applying an output of the SFP limiting amplifier to a low pass filter to improve the jitter tolerance. The low pass filter optionally applies a programmable amount of attenuation to high frequency components of the output. The low pass filter slew rate controls (i.e., rotates) a data eye representation of the received signal to increase the data eye representation along a time axis. The noise margin of the received signal can optionally be improved by applying an output of the low pass filter to an all pass filter. A slew rate controller can evaluate the data eye statistics to determine a setting for the low pass filter.
摘要:
Methods and apparatus are provided for improving the jitter tolerance in an SFP limit amplified signal. Jitter tolerance is improved in a communications receiver by applying a received signal to an SFP limiting amplifier; and applying an output of the SFP limiting amplifier to a low pass filter to improve the jitter tolerance. The low pass filter optionally applies a programmable amount of attenuation to high frequency components of the output. The low pass filter slew rate controls (i.e., rotates) a data eye representation of the received signal to increase the data eye representation along a time axis. The noise margin of the received signal can optionally be improved by applying an output of the low pass filter to an all pass filter. A slew rate controller can evaluate the data eye statistics to determine a setting for the low pass filter.
摘要:
Methods, systems and processor-readable media for reducing the width of a logical comparison. A width of a logical comparison based on a previous result generated can be recursively reduced from a data stream and a maximum count of consecutive ones or consecutive zeros determined from the serial data stream based on a priority encoder within a single clock cycle in order to avoid a use of complex functions. In this manner, the maximum number of the consecutive ones or the consecutive zeros in a parallel word bus within the single dock cycle can be ascertained.