Most test-equipment
manufacturers live on
the leading edge of electronics.
Their advanced
instruments give engineers
the tools to develop
the latest, limit-pushing circuits and
systems, because “you can’t design it if
you can’t test it.”
Today’s most advanced instruments
solve measurement problems at higher
frequencies and faster data speeds, and
they include much more sophisticated
automated testing features in software.
Now, these faster-sampling-rate, widerbandwidth,
software-based features are
finding their way into more general-purpose
bench instruments used on not-soleading-
edge designs.
Armed with such specs and features,
these bench instruments make more
common measurements a snap despite
the complexity. There’s no better example
of this than Tektronix’s MSO4000
series oscilloscopes.
ON THE BENCH
The MSO4000
mixed-signal oscilloscope is a small but
full-featured bench scope that generates
quick results for complex designs (Fig. 1).
This scope targets engineers who design,
test, and debug embedded controller
products with multiple serial interfaces, as
well as related digital circuitry.
The MSO4000 includes an impressive
digital signal test and analysis
feature that will almost make you
believe there’s no need for a logic analyzer.
Though it doesn’t contain a fullfeatured
logic analyzer, the MSO4000
provides 16 logic channels in addition
to a standard two or four analog
channels, providing more than
enough inputs to test nearly anything
you’re working on.
Virtually all of today’s electronic products
contain at least one embedded controller.
As a result, most engineers end
up spending lots of time testing and
debugging the microcontroller and anything
tied to it, such as the analog-todigital
converter. And, a standard oscilloscope
almost always comes up short
in embedded debugging because of the
limited number of signals it can display
simultaneously.
These days, the most crucial need for
designers is to look at the 8-bit data bus or
the 16-bit address bus. Viewing an FPGA’s
inputs and/or outputs is another common
challenge. A logic analyzer is the answer,
but fewer labs have these expensive and
complex devices. Often, they’re simply
overkill for the task at hand.
This is where the MSO4000 scopes
step in. They incorporate 16 digital
inputs and can display all of the signals
on screen at the same time (as well as up
to four analog signals). This feature
alone makes the scope a more versatile
instrument for any lab.
There are four versions of the
MSO4000. The MSO4034 and
MSO4032 have a 350-MHz bandwidth
and a 2.5-Gbit/s sampling rate. The
MSO4054 features a 500-MHz bandwidth
with 2.5-Gbit/s sampling rate.
The high-end model, which I tested, is
the MSO4104. It delivers a 1-GHz
bandwidth with a 5-Mbit/s sampling
rate. Those rates apply to all channels,
and all channels have a maximum
record length of 10 Msamples.
All of the scopes possess four analog
channels, except for the MSO4032,
which has two. Also, each scope contains
16 digital input channels, with
each channel featuring a timing resolution
of 60.6 ps (16.5 Gsamples/s).
Because most modern microcontroller
clocks push or exceed 100 MHz, you
need all of the resolution you can get to
resolve critical timing issues.
FEATURES GALORE
The userfriendly
screen on this scope measures
10.4 in. in an XGA format. Additionally,
you can easily see all 20 channels
clearly at one time or configure the
number of analog and digital channels
to fit your situation. The digital signals
are displayed with green high, blue low,
and white rise/fall, making them easier
than ever to interpret.
Another key feature is the Wave
Inspector, which allows you to capture
up to 10 million samples on each of the two or four channels. Subsequently, you
can search, pan, and zoom the waveforms
for closer inspection. It lets you
identify glitches faster and examine the
details of any signal by scrolling
through the captured records. This
works on the digital channels as well.
Also, there’s the ability to display bus
data as well as trigger and search on specific
data values. You can create up to
four parallel buses. Then, by specifying
which channels are the clock and data
lines, you can assemble a parallel bus
display that automatically decodes the
bus content. You can even trigger on bus
data values.
There’s optional support for I2C, RS-
232, SPI, and CAN serial buses, too.
Almost all embedded designs use at least
one of these serial buses. With the
MSO4104, you can capture, decode,
trigger on, and search for specific codes.
The hex values of words are displayed
along with the pulses.
This feature alone speeds up embedded
troubleshooting measurably. And
again, you can trigger on specific data
values. Moreover, you can view the
decoded parallel or serial bus data in
a listing format. In this format, specific
codes or data values are more
easily identified.
The scopes come with a variety of analog
probes that fit the bandwidth. The
digital probe is unique in that it’s
designed as two groups of eight probe
lines that are color-coded (Fig. 2). Those
color codes are duplicated on the screen
to help you identify the line.
As mentioned before, I recently tested
an MSO4104 and came away very
impressed. Having used many different
scopes over the years and spent hours
debugging embedded designs, I can personally
attest to how the scope simplifies
tasks. The optional serial-bus testing
features are worth every penny and
will more than pay for themselves in
reduced troubleshooting time.
Prices for these scopes range from
$8700 for the MSO4032 to $17,200 for
the MSO4104. The digital probe set is
included with all versions. Serial test
support is optional. All models are currently
available.