File name Oscilloscope Selection Tip 8_ Serial Bus Applications - Application Note 5990-9606EN c20130402 .p
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