DDR2 Embedded Logic Analyzer Software

The logic analyzer setup software (Tektronix refers to these as 'Support Packages') provides a quick setup of the logic analyzer channels and logic analyzer clocking/acquisition parameters. This software also provides protocol decoding of the DDR3 transactions for easy display and logic analyzer triggering/filtering.

In order for the logic analyzer to capture data, the DDR2 signals must be digitized. For the command and address bus, this process is relatively straightforward as the center of the valid data eyes align with rising edge of the DDR clock. For the DDR2 data bus signals, the process of determining the optimal sample position for digitization is much more complicated. The valid eyes are purposely skewed - as per the DDR2 specification - on a byte basis relative to the DDR clock. The valid eyes also contain skew (again relative to the DDR clock) on a bit basis due to unavoidable artifacts of high-speed designs and the timing variations caused by the digitizing of the signals based on the threshold.

These, among other factors, make reliable and accurate DDR2 read and write data bus acquisition extremely difficult - if done manually. NEX-DDR2-SPA, provided free with every Nexus Technology DDR2 embedded logic analyzer solution, automates this process enabling quick and reliable DDR2 read and write data bus acquisition in only minutes. For more information, please see the NEX-DDR-SPA product page.

There's a BIG difference between protocol decode and protocol violation analysis. Protocol decoding provides a static tabulation of command and address bus activity. This functionality is made available through the logic analyzer listing window using a Nexus Technology DDR2 support package/setup software. Performing a very different and powerful set of tasks, protocol violation analysis analyzes the entire logic analyzer memory, compiling statistical information and error reporting based on every command acquired.

This provides a global picture of the activity on the bus and - more importantly - analyzes every command to see that the protocol adheres to the JEDEC specification. Protocol violation analysis software is available for all Nexus Technology DDR2 embedded logic analyzer solutions. Please see theNEX-DDR-PROTOCOL product page for more information.

Every embedded solution comes with logic analyzer setup software (TLA support package). This setup software acquires/reconstructs the command/address bus and acquires/reconstructs the read write data from the data bus. The software also decodes and displays the bus protocol, shows the valid read/write data and provides easy DDR protocol triggering to quickly capture relevant data.

Every embedded solution also comes with the NEX-DDR-PROTOCOL software tool. This software provides statistical information and global bus activity to quickly give the user an overview of the DDR2 bus activity without having to revert to a listing or waveform window. The software also performs basic protocol violation checking. Advanced protocol violation checking is available for purchase separately. Please see the NEX-DDR-PROTOCOL product page for more information on this powerful tool.

The most readily available tool to assist in the analog validation process is the Tektronix Logic Analyzer's 20ps (50GHz) MagniVu timing. This 2.5us deep acquisition space, separate from state acquisition memory is simultaneously acquired with state data, and is typically filled with bus activity that occurred around the state trigger. A wealth of analog information can be found in this data, including: positive/negative pulse widths, signal skew, and data glitches. Activity that appears too short, too long, unreasonably skewed relative to another signal, or that contains glitches are indications that there is an analog characteristic of that signal that deserves further attention.

Another powerful analog validation feature is the Tektronix Logic Analyzer's Analog Mux capability. When paired with an oscilloscope, this feature enables analog visibility of every DDR2 signal probed by the interposer with a touch of a button. This feature comes with two significant limitations. First, there is no calibration specification for the channel-to-channel skew through the Analog Mux. Second, the signals are bandwidth limited to 3GHz. This limitation acts as a high speed filter, limiting the visibility of the signal's harmonics that are over 3GHz. For DDR2-1067, this filtering will cause artificial increases in the slew rates which appears as rising/falling edges that take longer to transition. The effect on the data eyes will be similar, showing a rounding effect. Although these limitations forces the user to use an oscilloscope component interposer for accurate DDR2-1067 analog validation, the importance of this tool for preliminary analog validation can not be understated. The ability of an digital validation engineer to quickly and easily assess the general analog health of a target can save an enormous amount of time and resources.

Tektronix discusses some of these topics in more detail in the application note, Debugging Timing Problems with a Logic Analyzer.