Programming Embedded Systems, 2nd Edition

Emulators

An in-circuit emulator (ICE) provides a lot more functionality than a remote debugger. In addition to providing the features available with a remote debugger, an ICE allows you to debug startup code and programs running from ROM, set breakpoints for code running from ROM, and even run tests that require more RAM than the system contains.

An ICE typically takes the place of—or emulates—the processor on your target board. (Some emulators come with an adapter that clips over the processor on the target.) The ICE is itself an embedded system, with its own copy of the target processor, RAM, ROM, and embedded software. In-circuit emulators are usually pretty expensive. But they are powerful tools, and in a tight spot, nothing else will help you get the debug job done better.

Like a debug monitor, an emulator uses a remote debugger for its host interface. In some cases, it is even possible to use the same debugger frontend for both. But because the emulator has its own copy of the target processor, it is possible to monitor and control the state of the processor in real time. This allows the emulator to support such powerful debug features as hardware breakpoints and real-time tracing. Additional information about in-circuit emulators can be found in the November 2001 Embedded Systems Programming article “Introduction to In-Circuit Emulators,” which can be found online at http://www.embedded.com.

With a debug monitor, you can set breakpoints in your program. However, these ...