File name 5990-4093EN English _ 2014-07-31 _ PDF 984 KB c20140922 .pdf
Strategies for Debugging Serial Bus
Systems with Ininiium Oscilloscopes
Who Should Read This Application Note?
This application note is for digital designers in R&D
working with both analog and digital components,
including microcontroller and DSP systems using serial
buses. This application note discusses the challenges
associated with and new solutions for debugging serial
bus designs including PCI-Express Generation 1, Inter
Integrated Circuit (I2C), Serial Peripheral Interface (SPI),
or Universal Serial Bus (USB).
The Keysight Technologies, Inc. Ininiium Oscilloscopes provide many of the features of protocol
analyzers such as decode listings and protocol speciic triggering. However, a good question is
"If protocol analyzers already exist, why is this capability needed?"
First of all, having a single instrument that provides the capabilities of an oscilloscope, logic analyzer
and protocol analyzer provides lots of advantages. First of all, there is the convenience of bench
space. Why crowd your bench with three instruments when one will do? Secondly, even if you happen
to have all three instruments handy, it is a hassle to turn on another instrument and set it up. A single
"All-in-one" instrument saves time.
Secondly, having a single instrument that provides both serial and analog capabilities means
that serial problems can be traced back to their root cause. For example, if there is inter-symbol
interference on a PCI-Express bus, the problem will show up as an invalid packet (and invalid
symbol) in the decode listing. Just point at the problem in the listing and the corresponding waveform
is shown on the screen. Without both serial and analog capabilities, it is dificult to tell what caused
the invalid symbol.
Another beneit of using oscilloscopes to debug serial buses is easy connectivity. There's no need for a
standard port or special IO for connectivity. In addition, oscilloscope probes are passive while protocol
analyzers typically provide re-transmit and re-timing. If physical layer problems exist, connecting the
protocol analyzer can mask them.
Finally, Ininiium Oscilloscopes are able to support a wide variety of protocols such as I2C, SPI, RS232,
USB and PCI-Express. So the oscilloscope doesn't just replace a single protocol analyzer; it replaces a
number of them. It is very common for Engineers to attempt to "mentally decode" waveforms because
they don't have the right protocol analyzer at hand. This new capability eliminates this dificult
03 | Keysight | Strategies for Debugging Serial Bus Systems with Ininiium Oscilloscopes - Application Note