Feature Oscilloscopes
that you are viewing the truest repre- sentation of the signal possible. This speeds debug and test time as well as increasing the quality and reliability of the end product.
Multiple instruments in one Fast waveform update rate is not the only benefit MegaZoom architecture provides oscilloscope users. This approach also allows other instrument functionality to be placed on the custom ASIC chip. Now, not only do you get a capability packed oscillo- scope, you also get an integrated Mixed Signal Oscilloscope (MSO) that adds digital timing channels, an integrated function generator and a serial protocol analyser. Each one of these instruments provides innovative new tools to help you more efficiently debug designs as well as have an all-in-one instrument instead of several different ones.
Oscilloscope
The oscilloscope is used to capture data. The more data it can capture at a high sample rate, the more detail can be viewed on the signals being tested. These days designs are doing more complex processes and often the oscil- loscope needs to capture long complex waveforms using the scope’s deep acquisition memory in order to get all the data. MegaZoom deep memory is architected to automatically select the best use of sample rate and deep memory to quickly capture large amounts of data. Manually scrolling through stored waveform data to find specific events of interest can be slow and cumbersome. However, if the oscilloscope has automatic search & navigation capa- bility, you can easily set up specific search criteria and then quickly navigate to ‘found and marked’ events using the front panel forward and back navigation keys. In the example shown in the screen image above, the scope was set up to capture a one millisecond time-span of a complex digital data stream. Using the scope’s Search & Navigation capabil- ity, it was able to find, mark (white triangles shows location of each runt), and then quickly navigate to 20 occurrences of ‘runt’ pulses. This saves hours of search time because you no longer have to manually search the, when you can find it in seconds automatically.
Mixed signal Oscilloscope Digital content is everywhere in today’s designs and traditional two and four channel oscilloscopes do not always provide enough channels for the job at hand. With an additional 16 integrated digital timing channels, there is now up to 20 channels of time- correlated triggering, acquisition and viewing on the same instrument. This allows for more flexibility in the tools available for debug by increasing the number of signals that can be viewed at one time giving a much clearer picture of the system being characterized. In some cases, using additional function- ality in an oscilloscope will slow down the waveform update rate or reduce the responsiveness of it by orders of magni- tude. This tradeoff does not occur in an oscilloscope with MegaZoom architec- ture due to the integration of the digital channels on the ASIC chip.
Built-in function generator An integrated 20 MHz function genera- tor is ideal for educational or design labs where bench space is limited and it becomes quite the art form to get all these different instruments up and running and most often talking to each other. It can be very time consuming and frustrating. With the function generator already integrated into the oscilloscope hardware itself, it is able to provide stimulus output of sine, square, ramp, pulse, DC, and noise waveforms to a device under test. And because it is integrated, that means only one set of instrument menus and inter- face to learn. This capability is also able to generate a variety of built-in training signals that can be used to teach electrical engineering and physics students what an oscilloscope does and how to perform basic mea- surements on the signals generated by the WaveGen capability.
MegaZoom architecture Oscilloscope mask testing works by comparing a captured waveform to a ‘mask’ that consists of an upper wave- form limit and a lower waveform limit. The captured waveform ‘passes’ if each point of the captured waveform falls in between the upper and lower limits and ‘fails’ if a point extends above the upper limit or falls below the lower limit. Mask testing is sometimes also referred to as ‘pass/fail’ or ‘go/no go’ testing because it provides a fast and easy way to test your signals to specified standards as it acquires a ‘golden’ waveform and then by defining the tolerance limits of the signal to create a test envelope. It automatically detects the waveforms that deviate from the standard. The fast update rate achieved with the MegaZoom architec- ture translates into a hardware-based mask testing implementation on the
measurement & sensors directory 2012-2013
Example of a hardware-based serial protocol decoding of an SPI and a UART bus on an Agilent 3000 X-Series
oscilloscope
Using the automatic search and navigate capability can save hours
oscilloscope and now enables millions of waveforms in one to three seconds. With traditional architecture, mask test- ing is software based and is at the mercy of the CPU, so testing millions of waveforms would take days.
Serial Protocol Analysis When the serial protocol analysis engine becomes integrated into the MegaZoom ASIC chip, it means that now the decoding is hardware-based compared to a software-based analysis in traditional oscilloscope architecture. Software post-processing techniques are slower and can even get as low as seconds per update. That’s especially true when using deep memory, which is often required to capture multiple packetized serial bus signals. And when analyzing multiple serial buses simultaneously, decode update rates can be even slower. With a hardware-based system, the decoding gets a huge speed boost and now has a much higher probability of capturing infrequent serial communica- tion errors due to the integration onto one chip with no trade off in waveform update rate. Sometimes it may be neces- sary to correlate data from one serial bus to another. This is best accomplished by decoding two serial buses simultane- ously and is able to display multiple busses at once of the captured data in a time-interleaved ‘Lister’ display (see Figure, below). The ability to correlate the serial protocol in a lister table format as well as see the raw signals below will give insight into entire system charac- terization in record time.
More capabilities
The innovation of engineering plays no favourites in this time of technological advances. Even a basic oscilloscope is host to break through technology that changes the way students will learn and the way engineers will work. As these products are able to offer more and more capabilities that reduce project test times at a price everyone can afford, the faster the new products oscilloscope help to design and test will change the lives of consumers around the world.
Agilent Technologies T: 0131 452 0200
www.home.agilent.com
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