Oscilloscope Selection Tip 8_ Serial Bus Applications - Application Note 5990-9606EN c20130402 [2].p part of Agilent Oscilloscope Selection Tip 8 Serial Bus Applications - Application Note 5990-9606EN c20130402 [2] Oscilloscope Selection Tip 8_ Serial Bus Applications - Application Note 5990-9606EN c20130402 [2].p, Agilent Oscilloscope Selection Tip 8_ Serial Bus Applications - Application Note 5990-9606EN c20130402 [2].pdf text manual preview

Text preview for : Oscilloscope Selection Tip 8_ Serial Bus Applications - Application Note 5990-9606EN c20130402 [2].p part of Agilent Oscilloscope Selection Tip 8 Serial Bus Applications - Application Note 5990-9606EN c20130402 [2] Agilent Oscilloscope Selection Tip 8_ Serial Bus Applications - Application Note 5990-9606EN c20130402 [2].pdf

Back to : Oscilloscope Selection Ti | Home

Oscilloscope Selection Tip 8:
Serial Bus Applications

Part 8 of a 12-part series

Tip 8 Select a scope that can trigger on and decode
serial buses to help you debug your designs faster.

Serial buses such as I2C, SPI, RS232/UART, CAN, etc., are pervasive in many of today's
digital and mixed-signal designs. Verifying proper bus communication along with analog
signal quality measurements requires using an oscilloscope. Many engineers and techni-
cians verify serial bus communication with an oscilloscope using a technique known
as "visual bit counting". But this manual method of decoding a serial bus can be time
consuming and prone to errors. However, many of today's DSOs and MSOs have optional
built-in serial bus protocol decode and triggering capabilities. If your designs include serial
Agilent's InfiniiVision 2000, 3000 bus technology, then selecting a scope that can decode and trigger on these buses can
be a significant time-saver to help you debug your systems faster.
and 4000 X-Series oscilloscopes
Most scopes on the market today that have serial bus analysis capabilities utilize software-
provide a broad range of serial based decoding techniques. With software-based decoding, waveform and decode-update
rates tend to be slow (sometimes seconds per update). This is especially true when using
bus analysis options with hard-
scopes with deep memory, which is often required to capture multiple packetized serial bus
ware-based protocol decoding. signals. And when analyzing multiple serial buses simultaneously, software techniques can
make protocol-specific decode update rates even slower.

Agilent's InfiniiVision Series oscilloscopes utilize hardware-based decoding to provide virtual
real-time updates. Faster decoding with hardware-based technology enhances scope usabil-
ity, and more importantly, the probability of capturing infrequent serial communication errors.

Figure 1 shows an example of an Agilent 3000 X-Series oscilloscope capturing and decoding
a CAN (Controller Area Network) serial bus, which is commonly used in many automotive and
industrial machinery applications, including medical diagnostics equipment. Below the wave-
form is the time-correlated decode trace that shows the contents of a single packet/frame of
data. The upper half of the scope's
display shows the "lister" display,
which provides decoded informa-
tion in a more familiar tabular
format; like a traditional protocol
analyzer. The lister display can also
be used to search and automati-
cally navigate to specific packets of
interest.

Figure 1: Triggering on and decoding a CAN serial bus
using an Agilent 3000 X-Series oscilloscope.
In addition to triggering on and decoding serial buses, it is often necessary to perform
eye-diagram mask test measurements on serial bits. This is especially important for
higher speed differential buses and/or buses that communicate over a long network.
With an eye-diagram display, all serial bits are overlaid and compared to a pass/fail
mask based on published industry physical layer standards/specifications. Figure 2
shows an example of an eye-diagram mask measurement on an ARINC 429 serial bus,
which is commonly used in many of today's commercial aircraft. With a mask test rate
of up to 200,000 waveforms/sec, the scope quickly captures return-to-zero (RZ) bits that
Figure 2: Eye-diagram mask test on an
exhibit insufficient amplitude as shown by the traces color-coded in red.
ARINC 429 serial bus using an Agilent 3000
X-Series oscilloscope.

Serial bus analysis capabilities available in
Agilent's InfiniiVision X-Series Oscilloscopes
If you are in the market today to purchase your next oscilloscope, Agilent Technologies'
newest 2000, 3000 and 4000 X-Series oscilloscopes come in various bandwidth models
ranging from 70 MHz up to 1.5 GHz. Available on these scopes is a broad range of serial
bus protocol analysis options:

Serial Bus Analysis Capabilities X-Series Availability
Description 2000X 3000X 4000X
CAN/LIN decode and trigger DSOX2AUTO DSOX3AUTO DSOX4AUTO
I