FAQ

Here’s a list of frequently asked questions about XJTAG and JTAG boundary scan.
For answers to common questions about specific products, please go to the relevant product page.

What is XJTAG?

XJTAG is an innovative boundary scan software and hardware suite that enables rapid testing, debugging and programming of complex embedded electronics. XJTAG products work with the JTAG test access protocol – built into FPGAs, CPLDs and most CPU devices – that enables testing interconnects on printed circuit boards.

XJTAG’s mission is to help engineers to complete PCB debug and testing quickly and easily, enabling customers to focus on developing better products faster and manufacturing them more cost-effectively.

See what world leading companies are saying about the XJTAG system.

What is the difference between JTAG and Boundary Scan?

None. JTAG, also referred to as Boundary Scan, is a test access protocol that is embedded into many chips. It is a set of IEEE standards (1149.x) that allow JTAG-enabled ICs from any manufacturer to be connected and accessed via a simple 4-signal interface.

By controlling devices from the inside, XJTAG’s Boundary Scan products give test access to thousands of circuit nodes on your circuit board, including pins under Ball Grid Array (BGA) devices, which are inaccessible to conventional probes.

JTAG is also used for processor debug/emulation and In-System Programming.

Read more: What is JTAG and how can I make use of it?

What do I need for JTAG Boundary Scan test?

In order to test a board using boundary scan you will need the netlist for the board and the BSDL file(s) for the JTAG compliant devices on the board. The methodology nature of boundary scan testing is to compare the data returned from a Device Under Test (DUT) with the design to which that board was built. The netlist gives us the information about the design and the BSDL file gives us information about which parts of that design can be controlled / monitored using boundary scan.

The XJTAG test system uses this information to generate a set of ‘test vectors’ that will stimulate the board in such ways that we will be able to verify as much of the manufacturing integrity of the board as possible. This test coverage extends beyond just the JTAG-compliant devices on the board by proving that the JTAG enabled devices can interact with those devices that don’t have any JTAG capability.

What is a JTAG compliant component?

Not all devices have JTAG capability. Typically processors, DSPs, FPGAs, CPLDs, some Ethernet devices and QDR RAM have JTAG interfaces, along with some ASICs. Devices such as RAM and flash typically do not have this capability.

For JTAG enabled devices XJTAG uses their capability as its control mechanism, in the same way that a bed-of-nails machine uses a test fixture as its control mechanism. We use those devices to drive the nets to which they are connected, and to monitor the values of those nets while tests are running.

What can be done if a component is not boundary scan compliant?

It is often possible to use JTAG enabled devices to interact with the functionality of non-compliant devices in order to give the best possible test coverage on a DUT. Consider the nets that run between a processor and a RAM device. These nets can be tested for short circuit faults by our automatic interconnection test – the system will stimulate one net and check to see if the driven value is read on any of the other nets. However this type of test cannot check for open circuit faults at either the processor or the RAM. Nevertheless, a test that writes data into the memory array of the RAM and then reads values back can be created, and this test can also check for open circuit faults at both devices.

There are situations where type of testing can go further – for example external connectors can often be tested by connecting a loopback cable and then sending and receiving data to verify the operation of nets which have no direct connection to the JTAG enabled devices on the board.

Is there a way to convert a non-compliant device to a compliant device?

Unfortunately this is not possible. JTAG boundary scan is something that the device manufacturer has to add to the device, it cannot be added at a later stage.

What is a BSDL file and where to get it?

XJTAG uses the information contained in a BSDL file to work out how to access a device in the JTAG chain. Boundary Scan Description Language (BSDL), based on VHDL , is used to describe how JTAG (IEEE 1149.1) is implemented in a particular device.

These files are often available for download from the website of the component manufacturer. Some manufacturers require an NDA in order to release these files but most make these files publicly available.

Here are some links to BSDL files from a range of device vendors.

What if there are non-standard cell types in my BSDL file?

Whilst the IEEE 1149.1 (JTAG) standard defines certain standard cell types for use in JTAG devices, some manufacturers use non-standard cell types, in which case additional information is needed by XJTAG to use the devices. Follow the link above to learn how to identify such devices and supply the additional information to the XJTAG system.

Can analog components (such as resistors, capacitors, inductors etc) be tested?

JTAG systems can do limited testing when it comes to analog devices – JTAG is a digital technology. A JTAG pin can be set high or low but the voltage driven onto the net is defined by the device being used. Similarly the JTAG device can capture (read) a digital value of 1 or 0 but it does not report whether a 1 is caused by a voltage of 3.3 V or 2.8 V.

Boundary scan allows checking whether a resistor is connecting two nets together, providing there is a mechanism to test for open-circuit faults on each side of the resistor. If for example the resistor is connecting a processor to a RAM then we will only be able to verify the connections to the RAM if the resistor is in place. However it would not be possible to use boundary scan to check whether it is a 0R resistor, a 100R resistor or even a 1K resistor as the JTAG compliant device would be able to drive signals through all of these values.

Similarly if there is a pull resistor on a net the undriven net’s digital value can be tested to be correct, depending on whether it is a pull-up or a pull-down. However the value of the resistor cannot be determined, so a 1K resistor would look the same as a 4.7K resistor to a boundary scan test.

Most capacitors on a Device Under Test are found in the power supply sections of the board, where typically JTAG access is poor. Others may have little effect on the low speed testing that boundary scan tests typically carry out. However some testing can be performed on inline coupling capacitors if the JTAG compliant devices on both sides of them support the newer 1149.6 JTAG standard. If full testing of these components is required then boundary scan testing should be combined with ICT for best results.

Starting your free evaluation

To help you evaluate XJTAG software and hardware boundary scan products for debugging, testing and device programming, we offer a 30-day trial period, with no obligation to purchase.

As soon as we hear from you, one of our test experts will contact you to discuss your end application and the evaluation process. We will then work with you to supply you with an XJTAG system when is most convenient for you.

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When will the product trial be available?

Depending on your timescales, we can target the trial to start when you are ready, any time from next day to next quarter. If you are looking to take advantage of our free test setup offer, then it’s good to plan ahead so we can schedule in the work.

Are there any limitations in the trial version?

The tools provided for evaluation are fully functional, so all features of the products are available for you to try out.

What is a Free Test Setup?

If requested, XJTAG will set up its test system and one development project on your own electronics when you take a 30-day trial.

Can I have the trial only, without the test setup?

Yes.

If I want a test setup with my trial, what do I need to supply?

To set up your board, we will require the following (under Non-Disclosure Agreement):

  • Circuit diagrams for the board as a PDF that can be searched.
  • Netlist(s). We support over 60 netlist formats (including RINF, EDIF, Protel, PADS-PCB and any ASCII netlists)
  • Details (including BSDL files) of custom JTAG-enabled parts fitted on the boards (if any).

Ideally, we prefer to get the tests up and running on your board. If you would like us to complete this last stage, we will also need access to a board.

What resources are available to help me evaluate the system?

The XJTAG system comes complete with an XJDemo board and interactive tutorials to get you started with developing your first test system with XJTAG.

You will have access to XJTAG’s device test libraries and latest S/W upgrades, during your evaluation period.

Can I get technical support or help for my trial version?

We are proud of our support and as with all aspects of the tools, during the evaluation, we encourage you to try it. We provide full technical support by telephone, email and web meeting, to help with the set up or troubleshoot any issues.

For additional help, we recommend searching the Knowledge Base, to find focused answers to specific questions.

How do I convert my trial to a purchased product?

If you already have the XJTAG Development System for evaluation, you can continue using the product without interruption by purchasing it. Simply contact your XJTAG distributor to make a purchase to have your hardware licence extended, and you can continue using XJTAG without reinstalling the software.

I have an earlier trial version. Can I convert it to the latest version?

If XJTAG has released new versions of its products since your trial and you are now ready to purchase, you will have access to download the latest version of the software.

What if I want to purchase only specific products, but not the full system?

XJTAG trials allow you to evaluate all of the tools that are part of the XJTAG Standard Development System, but you can certainly buy individual products that best match your business needs.

My evaluation licence has expired. Can I continue my evaluation for a further short period?

Possibly – contact us and we will consider your request.

My evaluation licence has expired and I no longer wish to use the XJTAG system. What should I do?

Please return your complete system to us and destroy any copies that you have made.

Can I run more than one version of XJTAG on the same computer?

You can install version 1.3.1.x alongside any older version of XJTAG: 1.0.x, 1.1.x, 1.2.x or 1.3.0.x. After version 1.3.1.x you can install XJTAG side-by-side with another version so long as the first 2 digits are different. For example, you can install 2.1.x.x alongside 2.2.x.x but you cannot install 2.1.8.x alongside 2.1.9.x.

Can I run XJTAG on a remote computer?

Yes. We regularly use Remote Desktop Connection and also web meeting software such as GotoMeeting, TeamViewer and WebEx.

Can I install XJTAG on my legacy Windows® system?

XJTAG is only supported under Windows 10®, Windows 8®, Windows 7® and Windows Vista® at the moment. Please upgrade to one of these operating systems before attempting to install XJTAG, and then apply the latest Service Pack for your operating System. Service Packs are available from Microsoft Support.

System requirements

Recommended:

  • Intel® Core i3, i5, i7 processor or equivalent (any generation)
  • Microsoft® Windows® 7, Windows 8.1 or Windows 10 (32 or 64 bit)
  • 4 GB of RAM

Please apply the latest Service Pack for your operating System. Service Packs are available from Microsoft Support.

How do I make sure my board has maximum test coverage?

We have produced a set of Design For Test (DFT) guidelines which explain what you need to take into consideration when designing your board, to make sure that as much of your board as possible is testable using JTAG.

Which CAD Netlist formats can XJTAG import?

XJTAG supports a wide range of netlist formats that the system automatically parses, identifies and accepts. These include RINF, Protel, PADS-PCB, Cadence Allegro, P-CAD, Genrad, BoardStation (Mentor), Zuken, Protel V2, EDIF 2 0 0 and many others.

You should be able to use any ASCII netlist; however if your netlist is not recognised, please contact XJTAG Support and we will be happy to convert it to a format that works and add a parser to a future release.

More about netlist formats on the XJTAG Blog.

How do I convert my trial to a purchased product?

If you already have the XJTAG Development System for evaluation, you can continue using the product without interruption by purchasing it. Simply contact your XJTAG distributor to make a purchase to have your hardware licence extended, and you can continue using XJTAG without reinstalling the software.

Once you have received your new licence code, use the Authorisation Codes utility to enter it into your XJLink.

How do I choose between hardware or network license?

XJTAG software licences can be held in the JTAG controller hardware that is used to connect to the board that is being tested, or on a network licence server.

Hardware Licensing

Holding the licence in a small JTAG controller unit such as the USB XJLink2 offers significant portability. XJTAG software can be installed on any number of PCs and used whenever the JTAG controller is connected.

Network Licensing

Portability can be extended still further using network licensing, if you need to have several hardware units but don’t need to use the software all the time on all of them. For example, if you have multiple production line setups, use the tools across multiple offices, or share development software for debugging occasional issues. Anyone who needs an XJTAG licence – from the design engineer to the repair technician – can check it out from the server and run the software they need.

If you are developing tests without your target hardware you can use a network licence to set-up your tests without having an JTAG controller connected. Then to run the tests connect an unlicenced JTAG controller and the network licence can be used to execute them. Once you close the software and stop using the licence it is released back to the server and can be used elsewhere in your organisation.

Keeping licences on the network server means that they are no longer tied to a particular location. The test capability offered by XJTAG can be accessed by any user in your organisation (given that there is one JTAG controller connected for board interaction).

Read more on network licensing.

Does it cost extra to upgrade to add another product later on?

No. Upgrading is simple and our costs are transparent with no penalty for adding functionality at a later date.

I have an earlier trial version. Can I convert it to the latest version?

If XJTAG has released new versions of its products since your trial and you are now ready to purchase, you will have access to download the latest version of the software.

Haven’t found what you are looking for? Please ask a question or contact us directly.

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