Abstract: A compensation circuit within the data transmission system compensates a signal for transmission media attenuation by amplifying the signal with a gain Gain=K0+K0.5f0.5+K1f1+K2f2+ . . . Knfn where f is signal frequency, n is an integer larger than 0, and coefficients K0, K0.5, and K1, K2 . . . Kn are adjustable. Coefficient K0 is adjusted to compensate for DC losses of the signal in the transmission media. Coefficient K0.5 is adjusted so that the term K0.5f0.5 compensates for skin effect losses of the signal in the transmission media. Coefficients K1, K2 . . . Kn are adjusted so that the n-term expression (K1f1+K2f2+ . . . Knfn) compensates for dielectric absorption losses in the transmission media. The compensation circuit may be used either as a pre-emphasis circuit by processing the signal before it is sent over the transmission media, or as an equalization circuit processing the signal after it is sent over the transmission media. In applications where skin effect losses are negligible, the term K0.5f0.

Abstract: A skew correction system incorporated into a transmitter forwarding a differential signal on a differential lane monitors returning signal reflections when the receiving end of the differential lane is appropriately terminated. Based on an analysis of the reflections, the skew correction system adjusts the relative timing of complementary edges of the differential signal departing the transmitter so as to substantially eliminate skew at the receiving end of the differential lane.

Abstract: A triggering circuit asserts a trigger signal in response to edges of a digital signal conveying a repetitive pattern of edges. The triggering circuit generates first data having a value identifying a position within the pattern of a last occurring edge of the digital signal and generates second data having a value identifying a position of a particular edge within the pattern that is to initiate a next assertion of the trigger signal. The triggering circuit asserts the trigger signal when the first and second data values match and de-asserts the trigger signal when the first and second data do not match. In a repetitive mode of operation, the triggering circuit keeps the second data value constant so that it always asserts the trigger signal in response to the same edge of the pattern.

Abstract: An electronic device under test (DUT) responds to a digital input signal by generating a digital DUT output signal conveying a repetitive digital signal pattern. An apparatus for measuring various characteristics of the DUT output signal includes a trigger generator for generating a series of trigger signal edges in response to selected DUT output signal edges occurring during separate repetitions of the digital signal pattern. The trigger generator can be configured to generate each trigger signal edge in response to the same or a different edge of the digital signal pattern. The apparatus determines when a DUT output signal edge occurs by determining when the DUT output signal rises above or falls below adjustable reference voltages. The apparatus alternatively responds to each trigger signal edge by measuring a period between two different edges of the digital signal pattern and or by repetitively sampling the DUT output signal to determine its state.

Abstract: An integrated circuit tester channel includes an integrated circuit (IC) for adding a programmably controlled amount of jitter to a digital test signal to produce a DUT input signal having a precisely controlled jitter pattern. The IC also measures periods between selected edges of the same or different ones of the DUT output signal, the DUT input signal, and a reference clock signal. Additionally, when the DUT input and output signals convey repetitive patterns, the IC can measure the voltage of the DUT input out output signal as selected points within the pattern by comparing it to an adjustable reference voltage. Processing circuits external to the IC program the IC to provide a specified amount of jitter to the test signal, control the measurements carried out by the measurement circuit, and process measurement data to determine the amount of jitter and other characteristics of the DUT output signal, and to calibrate the jitter in the DUT input signal.

Abstract: A jitter generator produces a jittery test signal for use in performing a jitter test on an integrated circuit (IC) device under test (DUT). The jitter generator includes a programmable delay circuit for delaying a non-jittery input signal with a varying delay controlled by input digital delay control data to produce the test signal. A pattern generator supplies a sequence of delay control data to the programmable delay circuit causing it to produce a desired jitter pattern in the test signal. During a calibration process, a measurement unit feeds the test signal back to the input of the programmable delay circuit, causing the test signal to oscillate with a period proportional to the delay through the delay circuit. The measurement unit then measures the period of the test signal for various values of delay control data and reports measurement results.

Abstract: A self-calibrating strobe signal generator for a BIST circuit responds to an edge of an input strobe signal by generating corresponding edges of first and second strobe signals separated in time by a target delay specified by input data. The strobe signal generator includes a multiplexer, a delay circuit and a controller. The multiplexer normally provides the input strobe signal as a multiplexer output signal to the delay circuit which generates edges in each of the first and second strobe signals in response to each edge in the multiplexer output signal with a programmable delay between corresponding first and second strobe signal edges.

Abstract: A portable device primarily for use in determining the effectiveness of various personal hearing protectors in attenuating hazardous noise. The device comprises an electronic circuit for generating audio test signals at varying amplitude levels, and a display for providing numerical indications usable to measure accurately the difference in amplitudes between the respective audio signals. The test signal increases or decreases in loudness in response to a subject-operated hand switch which also triggers display of the appropriate numerical indication at amplitude levels determined subjectively by the individual being tested. The electronic circuit of the device preferably is capable of producing such test signals in complex, multifrequency form with preweighting of the power spectrum of the signal so as to emphasize the most potentially hazardous frequencies.