Erratic trace measurements
There are several general problems that can cause erratic variations in trace
lists and inverse assembly failures.
Do a full reset of the target system before beginning the measurement.
Some designs require a full reset to ensure correct configuration.
Ensure that your target system meets the timing requirements with the
logic analyzer probe connected.
See “Capacitive Loading” in this chapter. While logic analyzer loading is
slight, pin protectors, extenders, and adapters may increase it to
unacceptable levels. If the target system design has close timing margins,
such loading may cause incorrect processor functioning and give erratic trace
results.
Ensure that you have sufficient cooling for the microprocessor.
Microprocessors such as the i486, Pentium
, and MC68040 generate
substantial heat. You should ensure that you have ambient temperature
conditions and airflow that meet or exceed the requirements of the
microprocessor manufacturer.
Capacitive loading
Excessive capacitive loading can degrade signals, resulting in incorrect
capture by the logic analyzer, or system lockup in the microprocessor. All
interfaces add additional capacitive loading, as can custom probe fixtures you
design for your application.
Careful layout of your target system can minimize loading problems and
result in better margins for your design. This is especially important for
systems that are running at frequencies greater than 50 MHz.
Remove as many pin protectors, extenders, and adapters as possible.
If You Have a Problem
Erratic trace measurements
A–6
Summary of Contents for E2470A
Page 8: ...1 Setting Up the Preprocessor Interface ...
Page 22: ...2 Analyzing the Motorola MC68HC16Y1 ...
Page 34: ...3 Preprocessor Interface Hardware Reference ...
Page 38: ...Block Diagram Preprocessor Interface Hardware Reference Theory of Operation and Clocking 3 5 ...
Page 56: ...A If You Have a Problem ...
