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Method for timing test hooks for testing dynamic phase tracking interpolator-based receivers

IP.com Disclosure Number: IPCOM000023840D
Publication Date: 2004-Mar-31
Document File: 10 page(s) / 98K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for timing test hooks for testing dynamic phase tracking interpolator-based receivers. Benefits include improved functionality, improved performance, and improved reliability.

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Method for timing test hooks for testing dynamic phase tracking interpolator-based receivers

Disclosed is a method for timing test hooks for testing dynamic phase tracking interpolator-based receivers. Benefits include improved functionality, improved performance, and improved reliability.

Background

         A conventional source-synchronous test scheme routes the clocks along with the data from one side of the link to the other. Testing methodologies with source-synchronous clocking using the movement of the strobes has been studied in great detail over the years. However, the source-synchronous approach cannot test plesiochronous clocking (see Figure 1).

General description

         The disclosed method includes timing test hooks and a test procedure for the dynamic phase tracking interpolator-based receivers used in recovered clock input/output (I/O) links. The test apparatus reconstructs a data eye by schmooing the time axis while tracking the incoming signal. This test method is generalized for plesiochronous and mesochronous clocking methods. In product I/O testing in the AC I/O loop-back mode, dynamic tracking can measure the effective eye opening or the jitter component of a unit interval.

Advantages

         Some implementations of the disclosed structure and method provide one or more of the following advantages:

•         Improved functionality due to enabling at-speed timing testing of recovered clock I/O links, while maintaining dynamic tracking of the interpolator-based receiver designs

•         Improved functionality due to providing a simple method to reconstruct a data eye at receiver input

•         Improved functionality due to being generalized for plesiochronous and mesochronous clocking methods

•         Improved performance due to requiring no strobes to function (works for recovered clock schemes)

•         Improved reliability due to providing improved product test using enhanced I/O loop-back schemes and link testing

Detailed description

         The disclosed method includes phase-tracking receiver functions, dynamic tracking, and a testing procedure.

 


Phase-tracking receiver functions

         A typical tracking sampling receiver samples the data bits using an interpolated clock that samples right at the center of the eye, designated as I. It also employs another clock, designated as Q, exactly quadratic to the in-phase clock. Clock I samples the data, and clock Q tracks the edges. In the lock condition, the tracking circuit continuously aligns the Q-clock phase to the data transition. Clock I is later rotated to sample the eye center detected in the received waveform. The sampled data is stored in first-in, first-out (FIFO) memory before being read out to the core after synchronization to the local clock (see Figures 2 and 3).

Dynamic tracking

         The input signal is sampled during periodic time windows. These sample bits, which occur during multiple phases of the local clock, are resynchronized to a single clock phase. The sample bits are passed to vote generation logic, which first detect...