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to Select the Right Bus Analyzers and Controllers
President - Saelig Co. Inc.
are Bus Analyzers and Controllers?
analyzer is a debugging tool, a hardware/software
combination used during development of hardware products or device
drivers for a specific bus, or for diagnosing bus or
product errors. The bus analyzer records the bus signals, decoding and
displaying the data. A bus
controller is often included,
adding the capability to drive the bus with specific, appropriate
signals, often simulating a missing device. Bus analyzers are vital
diagnostic tools in the design, development, and test of automated
systems. Analyzers can be plug-in boards or serial
PC-connected modules, or standalone units that capture and/or
stimulate bus activity. Features range from transparent logging to
full bus control and simulation, and include performance analysis, bus
event tracking, anomaly detection, simulated bus activity generation,
etc. Software included with the analyzer allows you to
setup test conditions and observe and analyze results.
Bus activity can be viewed
from two different perspectives: hardware and software.
Hardware analysis looks at the I/O activity from the aspect of
the physical bus. Hardware analysis can also provide you with the
ability to view the actual physical communications that occur on the
bus (e.g. handshaking between the host and target). If you want to
view detailed timing analysis, such as the time to send the command,
data, messaging, etc., then only a hardware analyzer can show you this
type of low-level detail. Software
analyzers look at the I/O activity from the operating system's
interpretation of those signals.
What are your bus needs?
probably have a specific problem you’re tackling, so make sure you
can analyze the appropriate bus protocol (e.g. serial busses like
RS232/422/485; I2C; SPI; CANbus; LINbus or PC system architecture
busses like PCI, PMC, cPCI, VME, PC/104, or wireless protocols like
Zigbee, WiFi, Bluetooth). It
pays to think toward the future and get an upgradeable product as new
Decide on a budget and needs/parameters.
Will a simple $100 bus
monitor suffice, or do you need to spend $25,000 on a sophisticated
standalone box for production verification?
Do you just need to see bus signals – in which case maybe a
scope or PC scope adapter will do (e.g. www.picotech.com,
This may help you debug issues like timing problems, slow rise-times
or excess bus capacitance, interference spikes, etc. Engineers
troubleshooting ever-faster serial buses encounter digital problems
caused by the actual quality of the data signal. Ideal digital pulses
have fast, clean transitions. At higher operating speeds, cable
terminations and reflections make it increasingly difficult to
maintain ideal signal characteristics.
Useful Scope/Logic Analyzer combinations can be found at
and www. http://www.usbee.com/
what the bus signals mean takes some software, so you can spend as
little as $100 for a simple “dongle” or as much as $25,000 on a
sophisticated standalone bus analyzer.
Using webs resources - how to search without
getting garbage links.
uses Google, but the results often contain too many spurious links to
be of much help. Add search words specific to your needs to cut down
on specious links. Of
course, you’ll be using http://www.besttest.com/
for a search, but this only works for manufacturers who’ve
discovered BestTest and submitted their information. Or go straight to
the listing of Test
Products and Services at http://besttest.com/BestTestDirectory/ProductDirectory/
if you go to a technical information site like www.eg3.com
and search on “bus analyzers” you get lots of references to just
one vendor – not helpful. Eg3 does, however, have great links to
most tech magazines for further research.
Much better resources are: http://www.electronicproducts.com/
since that’s where most manufacturers will send their product
Amazon’s search site www.a9.com
because it gives links plus a Wikipedia definition of your search term
USB 1.0 or
comments should help you find useful bus products more speedily.
So don’t get offended if your boss tells you that you need
to Select a Bus Analyzer
Schuh, Director of Military
Electronic Products, Condor Engineering
The wide range of protocols in use today in various
bus systems for military, avionics and other commercial applications
has brought about highly-efficient information exchange that is both
swift and accurate. This, in turn, has accelerated the demand for a
continuing evolution in bus analyzers. What follows are some essential
requirements that you will want to examine in selecting a suitable bus
- PC-Based Analyzers versus Box-Based Analyzers — A
distinct benefit of a PC-Based Analyzer, that includes the
graphical user interface (GUI) and an interface card, over the
Box-Based Analyzer, that may be anything from a handheld to
rack-mount device, is this: Not only will it perform protocol
checking but it also provides a very simple and easy way of
setting up terminals because of the GUI software that supports it.
Also, the ease with which you can set up data streams and data
buffers enable the importation of information into spreadsheets
such as Excel for spreadsheet and database manipulation. Another
plus for the PC-based approach is that the companion
software-based bus tools that are part of such analyzers brings
with it the ability to interpret data, including the ability to
perform engineering-unit conversion. This would be very difficult
to set up in a Box-Based Analyzer.
- Clear, User-Friendly Human Interface — Anyone
who uses a bus analyzer will expect it to be endowed with a very
clear icon-based human interface —
such as buttons and symbols — or tree-based presentations
of the bus components, as can be seen in Condor Engineering's
BusTools/1553 and BusTools/AFDX (www.condoreng.com).
A tree-based presentation is going to have the bus components and
their sub-features broken out, thereby providing the user with a
very clear representation of what he or she wants to do.
Furthermore, a bus analyzer should provide a detailed presentation
of bus activity while the analyzer is running. Included, as a bare
minimum, are just which components on the bus are seen, as well as
protocol errors and data errors that are occurring.
- Fulfills Three Distinct Functions — The
activities of a full-featured bus analyzer can be divided into
three categories: Logic-analyzer type functions, such as the
ability to trigger, enabling the user to set up separate files,
based upon certain activity patterns or events that occur on the
bus. A logic analyzer also filters, which means it can be
programmed to discard words or messages that are totally unrelated
to bus analysis. There is also the protocol-analyzer capability.
Whereas the third activity can be thought of system-level
troubleshooting, which is based upon interpretation and therefore
has the ability to evaluate the system data and set upper and
lower boundaries. System-level troubleshooting denotes that data
that is being transferred. For instance, a user may set up lower
and upper limits, say a lower limit of less than 45 units and an
upper value limit greater than 500 so that an alarm will be sent
whenever the value breaks these boundaries.
- Archiving Traffic — Another important feature
in a bus analyzer is the capability of archiving traffic off the
bus, which means the user can play back a particular activity. The
reason this is such an invaluable feature is that the user can
recreate a problem that has been observed by re-running it
repeatedly and then can appraise just how the data is performing.
A related feature, which can be found on some bus analyzers, is
the ability to play back to the interface bus, the screen or to
- Different Vantage Points — When examining
protocol and system-level analysis it is important to be able to
view activity from different vantage points. PC-based bus analyzer
tools provide you with many different ways to look at your
protocol and your system level analysis. For instance, we can use
a 'data watch' feature that allows one to actually graph the data
as it occurs. Multiple
comparative windows enable analysis of bus activity at different
points within the bus traffic, allowing comparison of messages
and/or the data. For instance, with some analyzers, such as Condor
Engineering BusTools, you can request a sequential view, which
displays the data that occurs contiguously within an inverted
stack. It displays the first message recorded, followed by a
sequence of other messages, which followed the first message. This
is sometimes called a 'sequential view' or a 'stacked view'.
- Simulation Ability — Another important requirement to consider in choosing a bus analyzer
is the ability to simulate the terminals related to your data bus
traffic. For instance, in MIL-STD-1553 you would want the
analyzer to simulate the bus controller or a remote terminal. This
means loading up the bus analyzer with data and errors that can
then be used to stimulate other components on the bus to learn
just how they will react.
in Selecting a Bus Analyzer
Renfro, Marketing Manager at VMETRO, Inc.
A Bus Analyzer is a pre-configured logic analyzer
conforming to the logical, electrical and mechanical specifications of
the target bus. These analysis tools are hard-wired to capture the
protocol of the target bus and offer formatted trigger setups and
trace displays. Typically a bus analyzer is a single board unit; thus
making it portable and ready-to-run. Bus Analyzers are available for
many standardized form factors including VME, PCI, PCI-X, PMC and
CompactPCI. When selecting a bus analyzer, engineers often consider
How do you
control the analyzer? Analyzer host connection methods vary
greatly from Ethernet to USB to RS-232. Interfacing to the analyzer
over Ethernet allows an engineer to connect to the analyzer from
anywhere, either locally or remotely. Thus, an engineer no longer has
to be located in the lab next to the equipment to debug. A remote
connection such as Ethernet also allows an engineering team to
troubleshoot issues for customers without going into the field which
saves time and money. An Ethernet connection can be established over
DHCP, fixed IP or VPN connections. Ethernet connection also allows
sharing of a bus analyzer between multiple engineers on a team.
trace buffer of sufficient size to capture the events of interest?
The trace buffer should be large enough to capture all transactions
required in diagnosing non-routine software problems. In addition to
the buffer size, the analyzer should be able to easily filter trace
data and acquire only data of interest to the engineer. If the
analyzer demultiplexes 64-bit Address, Data, Attribute (PCI-X only),
RMW (VME protocol), Command and Byte Enables (PCI/PCI-X protocols)
valuable trace buffer space can be conserved without setting
pre-acquisition filters. Some analyzers allow an engineer to filter
out cycles that are not of interest by changing the sampling options.
For example, retry cycles could be excluded when a device retries 8
times before the transaction occurs.
Some analyzers offer multiple trace views to
provide higher level views of trace data. Using one of these analyzers
would allow a software engineer working in PCI or PCI-X protocol to
view the transaction at a transaction level and then the engineer can
expand the transaction to see the actual data being transferred. This
same engineer is saving buffer space by not filling the trace buffer
with the details of the transactions (i.e. when FRAME#, IRDY# and TRDY#
assert). However, a hardware engineer trying to debug an issue may
need to see the transaction details. VMETRO’s Vanguard family of Bus
enables each engineer to use the sampling mode most appropriate for
to use is the analyzer? Download demonstration software and begin
getting familiar with the tool. The GUI software should be easy to use
and have all functions easily accessible. Try to set up triggers and
review sample trace data. Some bus analyzer vendors incorporate
extensive mnemonics for common signals. Some analyzers also allow the
user to set user defined mnemonics. For example, an engineer can name
each device that is being worked with. If the analyzer is very
powerful, it is beneficial to request a demonstration from the sales
contact to get up and running as quickly as possible. Evaluate the
product and the vendor’s support system. The documentation should
thoroughly explain each function in the analyzer. Determine if there
is additional information available to help familiarize new users with
the tool. Ask questions and provide feedback on how the tool works for
you during the evaluation.
functionality is available in the analyzer? When making the
investment in a test tool, it is important to review all functionality
available in the product, since the next project the engineer works on
may require additional functionality or another engineer on the same
project may need additional functionality. Typical additional
functionality available in bus analyzer tools includes API software
interfaces, statistics (Performance benchmarking tools), protocol
checking, exercisers and compliance testers. Sometimes additional
hardware or software is needed to perform all functions at one time.
analyzer function independently and concurrently with the statistics,
exerciser and protocol checker capabilities? To debug real world
problems, an engineer will want to run the analyzer at the same time
as the other functions. For example, to debug a software issue, an
engineer may need to run the analyzer triggering on the failure
condition, monitor statistics to see the performance of the system,
check for violations to the specification and generate bus
transactions with the exerciser. Some analyzers limit what functions
can be performed at the same time, so engineers have to work harder to
achieve the same information. VMETRO’s Vanguard Analyzers (www.vmetro.com/bus_analyzers)
enable each function to operate independently and concurrently to save
engineering hours in the debug process.
Conclusion: Bus Analyzers are designed to reduce the need for
detailed user knowledge of the bus protocol. Choosing an analyzer
which provides ease of use and decoding in the trace data will save
engineering hours as well as reduce the time required to debug complex
problems. Utilizing an Ethernet port allows engineers to remotely
debug problems in the field as well as work outside the laboratory. In
solving design problems, engineers often need more than just a passive
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