What is JTAG?


JTAG is an integrated method for testing interconnects on printed circuit boards (PCBs) that are implemented at the integrated circuit (IC) level.  Since its introduction as an industry standard in 1990, JTAG has continuously grown in adoption, popularity, and usefulness—even today, new revisions and supplements to the IEEE Std.-1149.1 standard are being developed and implemented. This document is a brief introduction to the nature and history of JTAG, from its introduction to new extensions in current development.

JTAG Technology

JTAG is commonly referred to as boundary-scan and defined by the Institute of Electrical and Electronic Engineers (IEEE) 1149.1, which originally began as an integrated method for testing interconnects on printed circuit boards (PCBs) implemented at the integrated circuit (IC) level. As PCBs grew in complexity and density—a trend that continues today—limitations in the traditional test methods of in-circuit testers (ICTs) and bed of nails fixtures became evident. Packaging formats, specifically Ball Grid Array (BGA, depicted in Figure 1) and other fine pitch components, designed to meet ever-increasing physical space constraints, also led to a loss of physical access to signals.

These new technology developments led to dramatic increases in costs related to designing and building bed of nails fixtures; at the same time, circuit board test coverage also suffered. JTAG/boundary-scan presented an elegant solution to this problem: build functionality into the IC to assist in testing assembled electronic systems.

Today, JTAG is used for everything from testing interconnects and functionality on ICs to programming flash memory of systems deployed in the field and everything in-between. JTAG and its related standards have been and will continue to be extended to address additional challenges in electronic test and manufacturing, including test of 3D ICs and complex, hierarchical systems.

History of JTAG

In the 1980s, the Joint Test Action Group (JTAG) set out to develop a specification for boundary-scan testing that was standardized in 1990 as the IEEE Std. 1149.1-1990. A few years later in 1993, a new revision to the standard—1149.1a—was introduced to clarify, correct, and enhance the original specification. An additional supplement, 1149.1b, was published in 1994 to add Boundary-Scan Description Language (BSDL) to the standard, paving the way for fast, automated test development and spurring continuous adoption by major electronics producers all over the world. The lessons that were learned became formalized in an update to the core standard in 2001 and IEEE-1149.1-2001 was published.

As new applications of JTAG were discovered, new standards were developed to extend the capabilities of JTAG. Standards such as the IEEE-1149.5 module test and maintenance bus standard in 1995 and the IEEE-1149.4 standard for mixed-signal testing in 1999 were met with low adoption rates and are not widely used at present. The IEEE-1149.6 standard introduced in 2003, on the other hand, began with slow adoption but has since become standard in many ICs as the technology it addressed—high-speed, AC-coupled signals—became a common feature of electronic systems. IEEE-1149.7, published in 2009 to address the need for JTAG in low-pin-count systems, is now standard on many popular microcontrollers.

Additional standards have also been published to add specific test capabilities. In 2002, the IEEE-1532 standard for in-system configuration of programmable devices was released and is now a common feature of FPGAs and their supporting software systems. IEEE-1581 was developed in 2011 to provide a convenient method of testing interconnects of high-speed memories with slow-speed test vectors; a version of this capability is implemented in some DDR4 memory components. To address the new application of combined capacitive sensing and boundary-scan test, IEEE-1149.8.1 was published in 2012. The extensibility of JTAG has been proven time and again.

More recently, efforts have been made to standardize JTAG access to instruments embedded within ICs. The IEEE-1149.1 standard was updated once more in 2013 for some housekeeping and to add extensions to access these instruments. Just one year later, an alternative standard for accessing these instruments, IEEE-1687, was published. Looking to the future, industry activities to extend JTAG into 3D-IC testing, system-level testing, and high-speed testing are already underway, proving that the versatility and extensibility of JTAG is here to stay.

How Does JTAG Work?

The JTAG/boundary-scan test architecture was originally developed as a method to test interconnects between ICs mounted on a PCB without using physical test probes. Boundary-scan cells created using multiplexer and latch circuits are attached to each pin on the device. These cells, embedded in the device, can capture data from pin or core logic signals as well as force data onto pins. Captured data is serially shifted out through the JTAG Test Access Port (TAP) and can be compared to expected values to determine a pass or fail result. Forced test data is serially shifted into the boundary-scan cells. All of this is controlled from a serial data path called the scan path or scan chain.

Because each pin can be individually controlled, boundary-scan eliminates a large number of test vectors that would normally needed to properly initialize sequential logic. Using JTAG, tens or hundreds of test vectors may do the job that had previously required thousands. Boundary-scan enables shorter test times, higher test coverage, increased diagnostic capability, and lower capital equipment cost.

The principles of interconnect test using boundary-scan components are illustrated in Figure 3. Two boundary-scan compliant devices are connected with four nets. The first device includes four outputs that are driving the four inputs of the other with predefined values. In this case, we assume that the circuit includes two faults: a short fault between Net2 and Net3, and an open fault on Net4. We will also assume that a short between two nets behaves as a wired-AND and an open fault behaves as a stuck-at-1 condition.

To detect and isolate defects, the tester shifts the patterns shown in Figure 3 into the first boundary-scan register and applies these patterns to the inputs of the second device.

Of course, interconnect testing is just one of many uses of JTAG—the aforementioned JTAG TAP has been extended to support additional capabilities including in-system-programming (ISP), in-circuit-emulation (ICE), embedded functional testing, and many more. The standard accounts for the addition of device-specific instructions and registers that can be used to interact with additional IC capabilities. For example, a microprocessor device may have embedded functionality for data download, program execution, or register peek-and-poke activities accessible using JTAG TAP; using the same tools, FPGA and CPLD devices can be erased, configured, read-back, and controlled using JTAG instructions through the IEEE-1532 standard. More recently, embedded IC instrumentation—from instruments that measure voltage and current to devices that can execute high-speed test on the chip—has used the JTAG TAP as the access mechanism, providing new visibility into the IC and further expanding the scope of JTAG testing.The input values captured in the boundary-scan register of the second device are shifted out and compared to the expected values. In this case, the results, underlined and marked in red on Net2, Net3, and Net4, do not match the expected values and the tester tags these nets as faulty. Sophisticated algorithms are used to automatically generate the minimal set of test vectors to detect, isolate, and diagnose faults to specific nets, devices, and pins.

JTAG for Product Life-Cycle Phases and Applications

While JTAG/boundary-scan was originally regarded as a method to test electronic products during the production phase, new developments and applications of the IEEE-1149.1 standard have enabled the use of JTAG in many other product life cycle phases. Boundary-scan technology is commonly applied to product design, prototype debugging, and field service as depicted in Figure 4.

The same test suite used to validate design testability can adapted and utilized for board bring-up, high-volume manufacturing test, troubleshooting and repairs, and even field service and reprogramming. The versatility of JTAG/boundary-scan tools delivers immense value to organizations beyond the production phase.

JTAG Test Basics

Most JTAG/boundary-scan systems are composed of two main components: a test program generator for test development and creation, and a test program executive for running tests and reporting results.

JTAG Test Program Generator

Test program generators accept computer aided design (CAD) data as input in the form of a netlist, bill of materials, schematic, and layout information. The test program generator (TPG) uses the information provided in these files, along with guidance from the test developer, to automatically create test patterns for fault detection and isolation using JTAG-testable nets on the PCB. Full-featured test program generation software will generally also include the capability to automatically generate tests for non-scannable components including logic clusters and memories that are connected to boundary-scan devices. A sample of faults that can be detected with automatically generated tests is shown in Figure 1.

JTAG Test Program Executive

Test program executives are used to run the tests created by the test program generation software. The test executive interfaces with the JTAG hardware to execute test patterns on a unit under test (UUT), then compares the results with expected values and attempts to diagnose any failures. Modern test executives include advanced features such as flow control, support for third party test types, and often include an application programming interface (API) for integration with additional test systems or development of simplified operator interfaces.

JTAG Benefits

The continuous drive toward higher density interconnects and finer pitch ball-grid-array (BGA) components has fueled the need for test strategies that minimize the number of test points required. By embedding the test logic within the IC itself and limiting the physical interface to just a few signals, JTAG/boundary-scan presents an elegant solution to testing, debugging, and diagnosing modern electronic systems.

Today, JTAG provides the access mechanism for a variety of different system operations. Just some of the benefits provided by JTAG are:

Reuse through the product life cycle. The simple access mechanism provided by the JTAG TAP can be used at all stages of the product lifecycle—from benchtop prototype debugging to high volume manufacturing and even in the field.

Test point reduction. JTAG provides test access through just 4 pins (2 pins for IEEE-1149.7 compliant devices), reducing the number of test points required, resulting in lower PCB fabrication costs and reduced test fixture complexity.

Independent observation and control. Boundary-scan tests operate independently of the system logic, meaning they can be used to diagnose systems that may not operate functionally.

Extensibility. JTAG has seen continuous development and new applications are frequently being discovered. Additional standards have been developed to address AC-coupled testing, reduced pin counts, and control of test instruments embedded within ICs.

JTAG Scan Chain Infrastructure Test

JTAG testing usually begins by checking the underlying infrastructure to ensure that all devices are connected and test capabilities are operational. Test patterns are used to exercise the instruction register and boundary-scan register for comparison against expected lengths and values. If present, device ID codes can also be read and compared against expected values to ensure that the correct component has been placed.

JTAG Interconnect, Bus Wire, and Resistor Tests

After verifying that the scan chain is working properly, test patterns can be used to verify interconnectivity between system components. Nets that involve three or more boundary-scan pins represent a special case, called a bus wire, where additional patterns can be used to isolate faults to a specific pin, as shown in Figure 2. During a buswire test, boundary-scan driver pins are tested one at a time to ensure that all possible opens are tested.

Devices that are transparent to DC signals can be modeled as “short” signal paths and included in the test; for example, series resistors can be tested for component presence and open faults, while directional buffers can be constrained and tested to ensure that signals sampled at the buffer output pins match the signals that are applied to the buffer input pins. Additionally, tests for AC-coupled signals can be integrated with interconnect and buswire tests in systems with IEEE-1149.6 standard components, allowing capacitors to be tested for AC signal transparency.

Special tests can also be used to check pull-up and pull-down resistors, ensuring that resistors are present in the assembled system in addition to testing the nets for open and short faults. To accomplish this, resistors are tested by first driving the signal to a state opposite the pulled value. The net is then tri-stated, allowing the resistor to pull the signal back to the original state. Finally, the signal is sampled and the value is compared to the expected pulled value.

JTAG Testing in Logic, Memory, & Complex Devices

Not only can interconnections between boundary-scan components and simple transparent components be tested, but additional non-boundary-scan components can be controlled and tested for functionality and continuity using connected boundary-scan components. Simple test patterns may be used to test logic devices such as decoders or multiplexers, while sophisticated scripts may be used control and test complex devices for basic or advanced functionality, including analog-to-digital converters, UARTs, and Ethernet PHYs.

A common application of a cluster tests uses the storage capability of RAM devices to verify interconnects between a boundary-scan device and a connected memory. Using a model of the memory component, tests can be automatically created to write specific data patterns to memory addresses and then read back and compared against the expected value. These patterns are designed to ensure that all memory data and address signals are driven to both high and low logic states. The same concept used to test RAM can also be applied to non-volatile memory, such as flash, EEPROM, and NVRAM components.

JTAG Testing throughout Product Lifecycle

While JTAG/boundary-scan was originally regarded as a method to test electronic products during the production phase, new developments and applications of the IEEE-1149.1 standard have enabled the use of JTAG in many other product life cycle phases. Boundary-scan technology is commonly applied to product design, prototype debugging, and field service.

The same test suite used to validate design testability can adapted and utilized for board bring-up, high-volume manufacturing test, troubleshooting and repairs, and even field service and reprogramming. The versatility of JTAG/boundary-scan tools delivers immense value to organizations beyond the production phase.

JTAG Embedded Test

Many modern processors use JTAG as the main interface for on-chip debugging (OCD), allowing the processor to be controlled over the JTAG port within an embedded system.

Using this same interface, the JTAG port can be used to initialize a processor, download and run a test program, and then obtain results; this test technique is a fast, convenient method for developing and executing peripheral tests and in-system-programming operations in embedded systems.

Because these tests run at the system processor speed, defects that may not be identified during low-speed execution can be detected.

In-System-Programming with JTAG

In addition to test applications, JTAG is also frequently used as the primary method to program devices such as flash memory and CPLDs. To program flash devices, the pins of a connected boundary-scan-compatible component can be used to control the memory and erase, program, and verify the component using the boundary-scan chain. FPGA and CPLD devices that support IEEE-1532 standard instructions can be accessed and programmed directly using the JTAG port.

Faster performance can be achieved using a CPU or FPGA to program the flash. In these cases, a small flash programming application is downloaded to the controlling device over the JTAG port, which is then used to interface between the test system and the flash programming application running on the embedded system. The program can run at much higher speeds than boundary-scan, increasing production throughput and rivaling or surpassing the speeds of USB and Ethernet-based programming solutions, without requiring an operating system or high-level software be present on the embedded system.

The IEEE-1149.1 JTAG team had the foresight to design an extensible standard—one that could employ additional data registers for many different applications. As a result, JTAG has grown from its original roots for board testing into a ubiquitous port that can be used for diverse applications such as in-system-programming, on-chip debugging, and more recently control of instruments embedded within ICs.

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Memory Foam Pregnancy Pillow

Is A Memory Foam Pregnancy Pillow Right Choice For You?

The Memory Foam Pregnancy Pillow is a great choice for pregnant women who are looking for comfort and support. It conforms to your body, and helps reduce back pain. Additionally, it is easy to store and transport, making it a great choice for on-the-go moms.

Memory foam pillows are all the rage these days. And for good reason – they’re incredibly comfortable and provide a lot of support. But are they the right choice for you during your pregnancy? There are a few factors to consider when making this decision, and we’ll explore them in detail in this blog post. From side effects to whether or not memory foam pillows are safe for pregnant women, read on to learn everything you need to know before making a purchase.

What is a Memory Foam Pregnancy Pillow?

Memory foam is a type of material that’s often used in mattresses and pillows. It’s a soft, cushiony material that helps to relieve pressure and pain from various parts of the body. One of the best things about memory foam is that it molds to your body shape, so you can get the most comfortable sleep possible.

A memory foam pregnancy pillow is a great choice for women who are looking for extra support during their pregnancy. Memory foam is designed to contour to your body, which helps to distribute your weight evenly and reduce pressure on your back, neck, and head. Plus, because memory foam is so soft and comfortable, you’ll be able to get a good night’s sleep even if you’re uncomfortable in other positions.

What Are The Benefits Of A Memory Foam Pregnancy Pillow?

Memory foam pregnancy pillows may offer some benefits over traditional pillows when it comes to comfort during your pregnancy. Memory foam is contoured to your body, which means it will conform to your shape and help reduce pressure and pain on your neck, back, and belly. A maternity bed might also come with a memory foam pregnancy pillow as part of the bedding set-up.

Additionally, memory foam is a natural material that helps regulate temperature. This can be particularly helpful if you are prone to hot flashes or night sweats. Plus, according to some experts, regular use of a memory foam pregnancy pillow may help improve Sleeping Apnea symptoms in pregnant women.

When choosing a memory foam pregnancy pillow, consider the following factors: firmness, size, shape, price point and reviews.

How To Choose The Right Memory Foam Pregnancy Pillow?

Memory foam pregnancy pillows are a great choice for pregnant women who want to sleep comfortably. There are a variety of models and sizes to choose from, so you can find the perfect pillow for your body type and sleeping style.

To choose the right memory foam pregnancy pillow, consider your needs. Do you want a medium-sized pillow or one that is extra large? Memory foam pregnancy pillows generally come in two sizes: standard (about 18 inches by 18 inches) and queen (about 23 inches by 23 inches). Consider your height and weight before making your purchase. A medium-sized pillow will work for most pregnant women, but if you are taller or heavier than average, go for a long pillow.

Another consideration is what type of memory foam pillow you want. There are two types of memory foam: traditional and hybrid. Traditional memory foam is made from polyurethane while hybrid memory foam is made from both polyurethane and micro beads, which give it more support than traditional memory foam. You can decide which type of memory foam is best for you based on your preferences and sleeping habits.

Finally, consider how important comfort is to you when shopping for a memory foam pregnancy pillow. For some women, the most important factor is firmness; others prefer softer pillows. In general, the softer the pillow, the less support it will provide. Consider how many hours per night you plan to sleep on your bed, as well as how much pressure you are comfortable with on your spinal cord and neck.

How To Use A Memory Foam Pregnancy Pillow?

Memory foam pregnancy pillows are considered to be the most comfortable type of pillow for expecting mothers. They are made from a material that molds to your body and supports your head, neck, and spine. Memory foam is known to offer support and comfort throughout your entire pregnancy.

To get the most out of your memory foam pillow, it is important to follow some simple guidelines:

First, make sure you have a firm yet comfortable mattress. This will ensure that your memory foam pillow will properly support your body. Secondly, adjust the pillow according to your body shape and size. You want it to be firm enough in the center but gentle on the sides of your head and neck. Finally, keep in mind that pregnant women generally need more support than usual because their bodies are expanding by up to 50%. Use this information as a guide when selecting a memory foam pillow for yourself or your partner.

At What Week Should You Start Using A Pregnancy Pillow?

If you’re pregnant, it’s important to find a pregnancy pillow that’s comfortable and supportive. A memory foam pregnancy pillow is a great option because it conforms to your body and provides support for your head, neck, and spine. You can start using one at around the seventh week of your pregnancy.

What To Avoid When Using A Memory Foam Pregnancy Pillow?

Memory foam pregnancy pillows are a popular choice for expecting mothers. They are designed to provide comfort and support during your prenatal days. However, there are some things you should avoid when using a memory foam pregnancy pillow.

First, make sure the pillow is firm enough. A too soft or floppy pillow may not support your head and neck adequately. Second, be careful if you have a neck or back issue. A too-soft pillow can cause pressure on your cervical spine and spinal cord which can lead to pain or discomfort. Third, try out the pillow before you buy it to ensure that it is the right size and shape for you. Fourth, keep in mind that memory foam pillows will conform to your body as you sleep so if you feel like it is too firm or hard; simply adjust the filling until you find a comfortable level of support. Finally, remember that pregnancy is an exciting time but don’t forget about your health! Make sure to take caution when using any type of bedding, including memory foam pillows.


Memory foam pregnancy pillows are a great way to ensure that you sleep comfortably throughout your entire pregnancy. Not only will this help you get the best rest possible, but it can also reduce the risk of developing lower back pain or other issues down the line. If you’re on the hunt for a comfortable and supportive pillow, be sure to consider a Sleepsia memory foam pregnancy pillow – they’re definitely worth considering!

body pillow

How To Use A Body Pillow During Pregnancy?

The Body Pillow is an essential piece of maternity equipment. It can help you sleep better and reduce the risk of various pregnancy-related problems.

Pregnancy is a time of great change for both you and your body. You’re growing and expanding, and your body is going through massive changes in order to support this growth. One of the most common changes you’ll experience is a change in sleeping habits. You may find that you need more space or support in order to sleep comfortably, which is where a body pillow can come in handy. In this blog post, we will discuss how to use a body pillow during pregnancy and what the benefits may be. We will also help you find the right one for your needs and give you some tips on how to care for it properly.

What Is A Body Pillow?

A Body Pillow is a type of pregnancy pillow that is designed to provide support and comfort while you are sleeping. They are made from different types of materials, including cotton, memory foam, and feathers.

How To Use A Body Pillow During Pregnancy?

If you’re looking for a comfortable way to sleep during your pregnancy, consider using a body pillow. Body pillows are designed to support your head and neck, which can help reduce pain in these areas. Here’s how to use one:

  1. Lie down on your back with your legs bent at the knee and feet flat on the ground. Place the body pillow between your legs so that it supports your lower back and hips.
  2. Pull the pillow up towards your chest, tucking it around your neck and shoulders. Use your hands to adjust the size and firmness of the pillow as needed.
  3. Close your eyes and relax into the pillow for a restful night’s sleep. If you find that the pillow is too hard or too soft, place another thin foam or futon mattress on top of it for added comfort.

Tips for Sleeping Better on a Body Pillow during Pregnancy

There are a few things to keep in mind when using a body pillow during pregnancy. First, make sure the pillow is comfortable and supportive. Second, be sure to adjust it regularly to ensure an optimal sleeping experience. Finally, consider using a pregnancy body pillow alongside other forms of prenatal support such as maternity pillow and bedding. Here are some tips for sleeping better on a body pillow during pregnancy:

1. Make sure the pillow is comfortable and supportive

When choosing a body pillow, make sure it is comfortable and supportive. It is important to find one that conforms to your body shape and size so you can get the best night’s sleep possible. To test whether the pillow is supportive, lie down on it and let your head rest on your hands. If you feel supported, the pillow should be okay for use during pregnancy.

2. Adjust it regularly

It is important to adjust the body pillow regularly throughout your pregnancy so that you can get an optimal sleep experience. To do this, simply press down on one end of the pillow so it becomes more pliable and then push up from below to increase its volume. This will help redistribute your weight evenly throughout your entire spine, which will improve your posture and help prevent back pain.

The Benefits of Sleeping on a Body Pillow during Pregnancy

There are a number of benefits to sleeping on a body pillow during pregnancy. Sleeping on a body pillow can help you stay comfortable during nighttime sleep, which is important for both you and your baby. You can also use a body pillow to support your neck and head while you’re sleeping. This can help reduce the risk of developing neck or head pain. And lastly, using a body pillow can improve your circulation, which is important for keeping your health overall improving. If you’re pregnant and are looking for ways to improve your sleep, consider sleeping on a body pillow from time to time.

How To Choose The Best Pregnancy Body Pillow?

Choosing the best pregnancy body pillow is essential to comfort during your upcoming pregnancy. There are a number of factors to consider, including your preferred sleeping position, size and shape of your body, and budget.

Here Are Four Tips For Choosing The Best Pregnancy Body Pillow:

  1. Consider your sleeping position: If you typically sleep on your back or side, a small, thin pillow may be more comfortable than a large, thick pillow.
  2. Size and shape matter: A maternity body pillow should be small enough to fit into any sleeping position but also big enough to provide adequate support. It should also be shaped comfortable so it conforms to your contours and helps you get a good night’s sleep.
  3. Budget is important: Body pillows range in price from $15 to $150+, so it’s important to find one that fits both your needs and budget. Some brands offer discounts during pregnancy, so be sure to check out their website or contact them directly for more information.
  4. Test it out before you buy it! Take the time to try out different types of pillows before making a purchase – this will help you find the perfect one for you!

How to Care?

When it comes to body pillows, there are a few things that you should keep in mind. First and foremost, you should make sure that the pillow is comfortable to sleep on. You should also make sure that the pillow is soft and has enough support. In addition, you should wash the pillow regularly to keep it clean and fresh. Finally, you should store the body pillow in a dry place when not in use.


If you’re looking to get a good night’s sleep during your pregnancy, using a body pillow can be a great way to do so. Not only will it help you rest comfortably, but it can also keep you from rolling off of your bed in the middle of the night. If you’re having trouble finding the right one for you, our selection at Sleepsia has a variety of options that should fit any taste and need.

WPC Fence

Benefits of WPC Fence

WPC Fence

WPC Fence is a composite material that is used as a fencing material. With the use of this material, you can make a fence that looks like wood but is stronger and more durable. This fence will not rot or splinter like real wood and it will not need to be replaced because of weather damage. WPC Fence also allows you to paint it any color you choose. You can have it painted to match your home or leave it in its natural color so that it blends in with your landscape.

The benefits of WPC Fence include:

Strength – WPC Fences are strong enough to withstand snow loads up to 100 pounds per square foot without bending or breaking. They are also resistant to fire, rot, termites and pests which makes them ideal for outdoor use.

Durability – WPC fences are resistant to moisture, wind and temperature changes which makes them ideal for outdoor use in any climate condition. They do not require much maintenance and last for many years without needing replacement parts or repairs.

Appearance – WPC fences look just like real wood but they are much stronger than actual wood so they will not warp or split when exposed to extreme heat or cold temperatures making them ideal for indoor or outdoor use. They are also resistant to water and stain so they will not splinter or fade when exposed to weather conditions.

WPC Fence in UAE is a great alternative to traditional wood fencing. It is made from 80% recycled materials and has the strength of concrete without the weight! The material is also termite resistant and rot proof so it will last much longer than regular wood fences.