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Method for synchronizing a signal Emissions Capturing Device to an internal signal in a microprocessor

IP.com Disclosure Number: IPCOM000029808D
Publication Date: 2004-Jul-13
Document File: 5 page(s) / 71K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for synchronizing a signal emission capturing device (ECD) to an internal signal in a microprocessor. Benefits include improved functionality and improved performance.

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Method for synchronizing a signal Emissions Capturing Device to an internal signal in a microprocessor

Disclosed is a method for synchronizing a signal emission capturing device (ECD) to an internal signal in a microprocessor. Benefits include improved functionality and improved performance.

Background

      Emissions capture is used to debug logic and speed paths in microprocessors. ECDs require synchronization with a clock of the signal to be captured. Additionally, ECDs require synchronization with a tester that stimulates a microprocessor with the required vector.

      Conventional ECDs require the averaging of the captured signal over thousands of iterations to generate a reliable estimate of the signal waveform. Each iteration must start/stop at the same point and the internal signal must transition at the same point through each loop or the waveform being averaged becomes corrupted. As a result, the production of quality waveforms is highly dependent on the jitter of the signal under observation. Jitter is the variation of the internal microprocessor signal with respect to the tester and the emission device’s clock each time through the measuring loop.

      In debug, a tester runs a series of vectors on the microprocessor. Eventually, a vector requires debugging. Because the ECD uses a small time frame to capture the signal, the tester provides capture start and stop information via a start signal and a clock. Four clock cycles correspond  to one vector on the tester. This time frame is the speed of the microprocessor’s data bus.

      Conventional solutions perform emissions capturing using a synchronization (sync) signal and a data clock directly from the tester to control the ECD. The tester provides the sync signal directly to the ECD. The tester also provides the data clock and bus clock independently to the microprocessor and ECD. Typically, a large amount of jitter (or signal noise) occurs between the internal microprocessor that is captured and the clock and sync signals sent to the ECD. The jitter makes the capture of a reliable waveform very difficult. Methods to reduce this noise by reconfiguring some circuits in the microprocessor have been unable to reduce it to acceptable levels.

General description

      The disclosed method includes techniques to synchronize internal signals in a microprocessor so they can be captured with a signal ECD, such as a laser voltage probe (LVP) or Time Resolved Emissions (TRE) machine. Additionally, the method includes techniques to use signals inside the microprocessor to provide the synchronization with the tester and the ECD. The signals provided by the microprocessor are a clock and a start pulse. This clock and start pulse will be generated from the same clock domain as the signal inside the microprocessor. This greatly reduces the jitter of the signal being tested with respect to the clock and start pulse.

              The key elements of the disclosed meth...