Embedded Systems Design: An Introduction to Processes, Tools, and Techniques
An easy-to-understand guidebook for those embarking upon an embedded processor development project.
TABLE OF CONTENTS Embedded Systems Design: An Introduction to Processes, Tools, and Techniques
Logic Analyzer
If you need to see what the processor is doing in real time, without significantly perturbing the system, you need to move to the next level of embedded systems debugging power, the logic analyzer. The logic analyzer is an extremely powerful tool for examining digital systems. Even so, there are problems with using logic analyzers with today s modern processors, which are discussed shortly. For now, let s focus on how you might use a logic analyzer to debug the real-time problems you encounter with an embedded system.
The logic analyzer has two basic modes of operation: timing and state. In timing mode, an internal high-speed clock determines when the memory of the logic analyzer takes a snapshot of the state of the processor, or processor and other digital signals in the system. A snapshot is just the voltage, or logic level, on every pin of the processor, taken at a sufficiently high capture rate so that you can see the timing relationships between the various processor bus signals.
| Note | In the previous paragraph, every pin really means every pin of interest. You would have no reason to probe the power supply voltage unless you thought it was noisy and causing problems. |
Timing Mode
In Figure 6.11, the logic analyzer is driven by a high frequency internal clock, perhaps 400MHz or faster. The processor clock in this example is 100MHz. Thus, for each cycle of the processor clock, you can record four samples of each pin of interest of the...
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