Erratic Trace Measurements - Agilent Technologies HP 1660E Series User Manual

Troubleshooting the Logic Analyzer
Analysis Probe Problems

Erratic trace measurements

There are several general problems that can cause erratic variations in
trace lists and inverse assembly failures.
❏ Ensure that the analysis probe configuration switches are correctly set for
the measurement you are trying to make.
Some analysis probes include configuration switches for various features
(for example, to allow dequeueing of the trace list). See your Analysis
Probe User's Guide for more information.
❏ Try doing a full reset of the target system before beginning the
measurement.
Some analysis probe designs require a full reset to ensure correct
configuration.
❏ Ensure that your target system meets the timing requirements of the
processor with the analysis probe installed.
See "Capacitive loading" in this chapter. While analysis probe loading is
slight, pin protectors, extenders, and adapters may increase it to
unacceptable levels. If the target system design has poor timing margins,
such loading may cause incorrect processor functioning, giving erratic
trace results.
❏ Ensure that you have sufficient cooling for the analysis probe.
Current processors such as the i486, Pentiumø, and MC68040 generate
substantial heat. This is exacerbated by the active circuitry on the analysis
probe. You should ensure that you have ambient temperature conditions
and airflow that meet or exceed the requirements of the microprocessor
manufacturer.
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