HP 64783A, User Manual

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Plugging The Emulator Into A Target System
The following paragraphs help you understand the emulator. Equivalent circuits
are shown, followed by a list of devices that you may need to use to overcome
mechanical and electrical constraints in your target system.
Understanding an emulator
An emulator is a tool intended for debugging software, and the interactions
between software and hardware. Although emulators can help in debugging certain
hardware problems, catastrophic problems often require use of other tools, such as
a timing analyzers with preprocessors, or oscilloscopes. To effectively use an
emulator, you need to understand its capabilities and limitations, and how it
interacts with your target system. This chapter discusses limitations and
interactions of an emulator, as they relate to your target system.
An emulator is designed to be electrically and functionally equivalent to the
processor it emulates, as much as possible. Most MC68040 signals are electrically
isolated from their counterparts on the target system connection. This is done for
both electrical and functional reasons. Equivalent circuits of each processor signal
are shown later in this chapter. The impacts of these circuits are calculated and
presented in the emulator specifications listed in Chapter 16, "Specifications and
Characteristics".
In the ideal case, you would use the emulator specifications listed in this manual
when designing your target system, instead of using the processor specifications.
In the typical case, your target system has already been designed and prototyped. A
target system that is designed around MC68040 worst-case specifications will
typically work with the emulator. If certain circuits in your target system do not
allow for variations in the MC68040 specifications, compare the relevant emulator
specifications to evaluate their impact on your target system. By keeping the
differences between emulator specifications and processor specifications in mind
while you design your target system, you can save hours of debugging time when
you plug the emulator into your target system.
The MC68040 emulator does not switch between large and small buffer modes like
the MC68040 processor does. The emulator internally uses the large buffer mode
to get optimum timing performance. Since these large drivers can cause problems
Chapter 18: Connecting the Emulator to a Target System
Plugging The Emulator Into A Target System
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