[stextbox id=”info” caption=”When is a dedicated protocol analyser needed?”]
Deep memory. Applications requiring very deep memory captures require a protocol analyser. Some protocol analysers can have very deep memory of the order of 72 GB, whereas oscilloscopes have maximum 2 GB.
Large number of lanes. When decoding a large number of data lanes simultaneously in a serial bus, engineers need to use a protocol analyser. They can see all the 16 lanes in a PCIe x16 link by using a protocol analyser, whereas oscilloscopes decode one lane at a time.
Specialised capabilities. Protocol analysers often have specialised performance analysis capabilities that go well beyond just triggering and decoding. For example, in case of PCI Express, one would need a protocol analyser to analyse a state machine called LTSSM.
Jammers and exercisers. Some applications might require serial link jamming, which means deliberate insertion of errors in the link. In this case, a jammer would be needed. Also, some applications might require handshakes between the instrument and the device under test, in which case an exerciser might be needed. Jammers and exercisers are normally used with dedicated protocol analysers, not with oscilloscopes.
—Sanchit Bhatia, Digital Applications Specialist, Agilent Technologies
[/stextbox]
Sanchit Bhatia, digital applications specialist, Agilent Technologies, explains the various advantages of using oscilloscopes for protocol analysis: “First, this saves the bench space and investment in a separate protocol analyser for each serial bus. Second, using a single instrument saves time as time and effort associated with the learning curve for each protocol analyser is removed. Third, oscilloscope-based protocol analysers have an inherent and unique capability of displaying protocol decoding correlated with the physical-layer analogue waveform. This correlation helps to trace back serial problems to their root cause in the analogue waveform. Finally, oscilloscopes provide easy connectivity to serial buses through a variety of probing options and fixtures. There is no need for a standard port or special input/output port for connectivity.”
Better graphical user interface
Protocol analysers with graphical user interfaces (GUIs) are gaining popularity among engineers due to their ease of use. The improved GUIs allow the users to execute test setups very quickly, resulting in improved productivity.
“User interfaces for these tools are becoming more and more user-friendly in the way they display decoded data, and hence protocol intricacies can now be dealt easily even with basic knowledge of protocol. It makes the task of test engineers fast and easy, while still maintaining the accuracy of testing. Some tools also support automation scripts for testing and analysis, which further helps reduce efforts and improve accuracy,” explains Siddharth Patel, lead engineer-embedded software, EATON India Engineering Centre.
More intuitive GUIs also have the advantage of reducing the learning curve for an engineer, translating to more productivity on the whole.
[stextbox id=”info”]Real-time feedback allows developers to capture, display and filter data instantly instead of waiting for the capture to download. With the data shown immediately on the screen and the engineer ready to perform interactive analysis with the captured data, the engineer’s efficiency level can increase as a tool that matches their development pace is utilised —Derek Fung, VP-Business, Total Phase, Inc[/stextbox]
“The embedded engineers are often required to monitor analogue and digital signals and some protocol analysis. Serial protocol analysis on digital channels enables viewing of analogue, digital and protocol analysis. To top it all, RTO’s intuitive user interface helps engineers to observe all these signals easily with drag and drop, gestures, etc,” explains Srinivasa Appalla, area manager, product support & applications, Test & Measurement, Rohde & Schwarz India.
Improved hardware
Design engineers do not want to be impacted by slow tools. Rather, they need tools that will move with their development speed as they iteratively test and debug their systems.
“One of the most valuable features of a protocol analyser is its ability to provide real-time feedback. Real-time feedback allows developers to capture, display and filter data instantly instead of waiting for the capture to download. With the data shown immediately on the screen and the engineer ready to perform interactive analysis with the captured data, the engineer’s efficiency level can increase as a tool that matches their development pace is utilised,” explains Fung.
Removing sluggishness while decoding helps improve the quality of work as well. Siddharth adds, “Instead of just software-based analysers, we now see more and more hardware-based protocol analysers with sophisticated PC user interface. Hardware analysers help in getting real-time stamp for frames and hence have very realistic picture of what is happening on the bus and when it is happening. With increasing buffer space on hardware and fast communication interface with PC software, these tools can capture a good amount of traffic continuously even with loaded bus.”
