Oscilloscopes store 8-bit values representing the voltage levels for a signal. Therefore, capturing one million samples across four oscilloscope probes requires 4 MB of memory inside the scope.

Logic analyzers sacrifice the detailed voltage measurements provided by oscilloscopes so that a greater number of digital signals can be analyzed together. A logic analyzer stores a single bit representing whether each input signal is above or below a specific voltage level. Therefore, a logic analyzer with 4 MB memory captures one million samples across 32 signals.

In essence, a logic analyzer is an extremely fast digital data acquisition device. Unlike simple data acquisition cards, logic analyzers can detect when the input signals match certain conditions. This permits logic analyzers to stop running (called a trigger) at a specific moment of interest. For example, to capture the events preceding an intermittent address bus error.

Timing analysis is analogous to how an oscilloscope captures data. The GoLogic™ samples its data inputs using a fixed sampling rate. The sampling rate is typically 5x to 10x faster than the input signal's clock speed. Although the GoLogic™ cannot display actual voltage values like a scope, timing analysis still exposes timing flaws that can occur between the input signals.

Transitional timing analysis is similar to "normal" timing analysis described above. As before, the GoLogic™ "oversamples" the data inputs at a fixed rate, usually 5x to 10x faster than the input signal. However, the GoLogic™ stores data to memory only when a transition occurs on at least one input signal. Therefore, periods of inactivity (where no transitions occur) do not waste the logic analyzer's memory depth. Transitional timing analysis is ideal for capturing data where long periods of inactivity may occur (such as a serial bus). Transitional timing analysis greatly increases the logic analyzer's effective memory depth. The time spanned by the data can be much greater even if fewer samples are acquired.

When using transitional timing analysis, the GoLogic™ records each sample's elapsed time using a 32-bit "time stamp" value. Half the memory depth is used to store the trace data while the other half contains the time information. Even though fewer samples are stored, transitional timing analysis can capture a much larger time-window than "normal" timing analysis.
 

What is State analysis?

State analysis uses a clock signal provided by the device-under-test to drive the GoLogic™. The logic analyzer stores a sample on the external clock source's rising (or falling) edge. Since no "oversampling" occurs, state analysis does not expose timing errors that may occur between signals. The trade-off is that state analysis optimizes the number of "states" the logic analyzer captures.