Ieee 1149.1 pdf

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JTAG (IEEE /P) Tutorial - Intermediate. AL 10Sept (JTAG )soundofheaven.info TI Test Symposium. The Test Access Port. TI warrants performance of its semiconductor products and related software to the specifications applicable at the time of sale in accordance with TI's standard. IEEE JTAG. Boundary Scan Standard. • Bed-of-nails tester. • Motivation. • System view of boundary scan hardware. • Elementary scan cell. • Test Access.


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IEEE (JTAG) Boundary-Scan Testing in Stratix III Devices, Stratix III Device Handbook, Volume 1, Chapter PDF: ISBN SS No part of this publication may be . (This introduction is not part of IEEE Std , Standard Test. Device Boundary-Scan Description Language (BSDL) files and other information regarding Texas Instruments IEEE Std. /JTAG/boundary-scan products.

Related Papers. Nexus defines a processor debug infrastructure which is largely vendor-independent. All articles with unsourced statements Articles with unsourced statements from October Articles with unsourced statements from June Articles with unsourced statements from June All articles with specifically marked weasel-worded phrases Articles with specifically marked weasel-worded phrases from March Articles containing potentially dated statements from All articles containing potentially dated statements Use dmy dates from March Although there are many possible BP program execution. Gustavo R Alves. That scan chain modification is one subject of a forthcoming IEEE From Wikipedia, the free encyclopedia.

In this mode the user may specify a BP condition and b provide control to the embedded microprocessor run the microprocessor program until the condition clock line in order to single step, stop or resume the becomes true.

Although there are many possible BP program execution.

Pdf ieee 1149.1

The control must be independent e. Also it must be possible to resume the microprocessor normal activity by placing the cell associated with the clock line in a bypass mode, without causing any spikes on the transition that could have hazardous effects. A simple circuit based on a Flip-Flop may be used to fulfil this precaution.

Access to internal registers and embedded memories inside or outside the microprocessor core. To implement requirement c the debug and test infrastructure of the embedded microprocessor must have access and control to the program memory internal or Fig.

Embedded DBMs connected to some of the external to the microprocessor , internal registers and both microprocessor lines. The scheme presented in figure 2 allows the implementation of this requirement. The internal registers To implement requirements d and e it is necessary to and memories program or data of the embedded embed, as illustrated in figure 3, the core of one or more microprocessor can be accessed through an internal scan devices called Digital Bus Monitors DBMs or 74SN chain.

JTAG - Wikipedia

A private BST instruction can be used to place the [9, 10]. Other embedded memories program or compared against the patterns sampled at the 16 input data data that are exterior to the microprocessor can be accessed lines.

The vector represents the value expected and the through the BS register, using for instance the EXTEST mask contains information regarding which bits are relevant instruction. If other embedded blocks have access to these e. The number 4. Conclusion of DBMs that have to be embedded depends on the microprocessor address and data bus width. If several The inclusion of an embedded debug and test DBMs are needed then they should be daisy chained e.

The device TAP pins may be used together. The sampled values are stored in the DBM for board production test and internal circuits debug. The internal memory identified as RAM in the block diagram embedded debug and test infrastructure includes the special presented in figure 4 whose contents can be scanned out microprocessor BST infrastructure, the embedded DBMs through the TAP.

The special microprocessor BST infrastructure contents, thus reducing the number of bits that have to be allows independent control of the reset and clock lines and shifted out in certain cases. The embedded DBMs allow monitoring and sampling in real time the address and data bus in order to detect the BP or the transition condition.

The samples can be stored in a dedicated memory whose contents may be shifted out through the embedded debug and test infrastructure. The proposed debug and test infrastructure can be first implemented in a PCB containing the DBMs and the circuit that will be integrated using the appropriated CAD tools and core libraries.

This solution allows a straightforward approach to the embedded circuit debug and test. The JTAG state machine can reset, access an instruction register, or access data selected by the instruction register.

Sometimes there are event signals used to trigger activity by the host or by the device being monitored through JTAG; or, perhaps, additional control lines. When exploited, these connections often provide the most viable means for reverse engineering. Reduced pin count JTAG uses only two wires, a clock wire and a data wire.

This is defined as part of the IEEE The two wire interface reduced pressure on the number of pins, and devices can be connected in a star topology. Other two-wire interfaces exist, such as Serial Wire Debug. The picture above shows three TAPs, which might be individual chips or might be modules inside one chip.

Pdf ieee 1149.1

A daisy chain of TAPs is called a scan chain , or loosely a target. Scan chains can be arbitrarily long, but in practice twenty TAPs is unusually long. So at a basic level, using JTAG involves reading and writing instructions and their associated data registers; and sometimes involves running a number of test cycles.

Most JTAG hosts use the shortest path between two states, perhaps constrained by quirks of the adapter. For example, one adapter [ which? Some layers built on top of JTAG monitor the state transitions, and use uncommon paths to trigger higher level operations.

Instruction register sizes tend to be small, perhaps four or seven bits wide. Two key instructions are:. This allows JTAG hosts to identify the size and, at least partially, contents of the scan chain to which they are connected.

So the bits not written by the host can easily be mapped to TAPs. It could for example identify an ARM Cortex-M3 based microcontroller, without specifying the microcontroller vendor or model; or a particular FPGA, but not how it has been programmed.

That way all TAPs except one expose a single bit data register, and values can be selectively shifted into or out of that one TAP's data register without affecting any other TAP.

The IEEE Some of these instructions are "mandatory", but TAPs used for debug instead of boundary scan testing sometimes provide minimal or no support for these instructions. Devices may define more instructions, and those definitions should be part of a BSDL file provided by the manufacturer. Devices communicate to the world via a set of input and output pins. By themselves, these pins provide limited visibility into the workings of the device.

However, devices that support boundary scan contain a shift-register cell for each signal pin of the device. These registers are connected in a dedicated path around the device's boundary hence the name. The path creates a virtual access capability that circumvents the normal inputs and outputs, providing direct control of the device and detailed visibility for signals.

Commercial test systems often cost several thousand dollars for a complete system, and include diagnostic options to pinpoint faults such as open circuits and shorts. They may also offer schematic or layout viewers to depict the fault in a graphical manner.

To enable boundary scanning, IC vendors add logic to each of their devices, including scan cells for each of the signal pins. These cells are then connected together to form the boundary scan shift register BSR , which is connected to a TAP controller. Overhead for this additional logic is minimal, and generally is well worth the price to enable efficient testing at the board level. An example helps show the operation of JTAG in real systems. This is a non-trivial example, which is representative of a significant cross section of JTAG-enabled systems.

Also read: IEEE 80 2013 PDF

Licensees of this core integrate it into chips, usually combining it with other TAPs as well as numerous peripherals and memory. Examples of such chips include:. Those processors are both intended for use in wireless handsets such as cell phones, which is part of the reason they include TAP controllers which modify the JTAG scan chain: Debugging low power operation requires accessing chips when they are largely powered off, and thus when not all TAPs are operational.

That scan chain modification is one subject of a forthcoming IEEE This debug TAP exposes several standard instructions, and a few specifically designed for hardware-assisted debugging , where a software tool the "debugger" uses JTAG to communicate with a system being debugged:.

That model resembles the model used in other ARM cores. One basic way to debug software is to present a single threaded model, where the debugger periodically stops execution of the program and examines its state as exposed by register contents and memory including peripheral controller registers. When interesting program events approach, a person may want to single step instructions or lines of source code to watch how a particular misbehavior happens.

After saving processor state, it could write those registers with whatever values it needs, then execute arbitrary algorithms on the CPU, accessing memory and peripherals to help characterize the system state.

Debug mode is also entered asynchronously by the debug module triggering a watchpoint or breakpoint, or by issuing a BKPT breakpoint instruction from the software being debugged. When it is not being used for instruction tracing, the ETM can also trigger entry to debug mode; it supports complex triggers sensitive to state and history, as well as the simple address comparisons exposed by the debug module. Asynchronous transitions to debug mode are detected by polling the DSCR register.

This is how single stepping is implemented: Modern software is often too complex to work well with such a single threaded model. ARM processors support an alternative debug mode, called Monitor Mode , to work with such situations. This is distinct from the Secure Monitor Mode implemented as part of security extensions on newer ARM cores; it manages debug operations, not security transitions. In those cases, breakpoints and watchpoints trigger a special kind of hardware exception, transferring control to a "debug monitor" running as part of the system software.

This monitor communicates with the debugger using the DCC, and could arrange for example to single step only a single process while other processes and interrupt handlers continue running.

Microprocessor vendors have often defined their own core-specific debugging extensions. If the vendor does not adopt a standard such as the ones used by ARM processors; or Nexus , they need to define their own solution.

Therefore, both software and hardware manufacturing faults may be located and an operating device may be monitored. The scan chain mechanism does not generally help diagnose or test for timing, temperature or other dynamic operational errors that may occur. The ability to perform such testing on finished boards is an essential part of Design For Test in today's products, increasing the number of faults that can be found before products ship to customers. A JTAG interface is a special interface added to a chip.

Depending on the version of JTAG, two, four, or five pins are added.

Pdf ieee 1149.1

The four and five pin interfaces are designed so that multiple chips on a board can have their JTAG lines daisy-chained together if specific conditions are met.

In either case a test probe need only connect to a single "JTAG port" to have access to all chips on a circuit board.

The TRST pin is an optional active-low reset to the test logic, usually asynchronous, but sometimes synchronous, depending on the chip. If the pin is not available, the test logic can be reset by switching to the reset state synchronously, using TCK and TMS. Note that resetting test logic doesn't necessarily imply resetting anything else.

There are generally some processor-specific JTAG operations which can reset all or part of the chip being debugged. Since only one data line is available, the protocol is serial. The clock input is at the TCK pin. Different instructions can be loaded.

Instructions for typical ICs might read the chip ID, sample input pins, drive or float output pins, manipulate chip functions, or bypass pipe TDI to TDO to logically shorten chains of multiple chips. As with any clocked signal, data presented to TDI must be valid for some chip-specific Setup time before and Hold time after the relevant here, rising clock edge.

Faster TCK frequencies are most useful when JTAG is used to transfer lots of data, such as when storing a program executable into flash memory. The JTAG state machine can reset, access an instruction register, or access data selected by the instruction register. Sometimes there are event signals used to trigger activity by the host or by the device being monitored through JTAG; or, perhaps, additional control lines.

When exploited, these connections often provide the most viable means for reverse engineering. Reduced pin count JTAG uses only two wires, a clock wire and a data wire.

This is defined as part of the IEEE The two wire interface reduced pressure on the number of pins, and devices can be connected in a star topology. Other two-wire interfaces exist, such as Serial Wire Debug.

The picture above shows three TAPs, which might be individual chips or might be modules inside one chip. A daisy chain of TAPs is called a scan chain , or loosely a target.

Scan chains can be arbitrarily long, but in practice twenty TAPs is unusually long. So at a basic level, using JTAG involves reading and writing instructions and their associated data registers; and sometimes involves running a number of test cycles. Most JTAG hosts use the shortest path between two states, perhaps constrained by quirks of the adapter. For example, one adapter [ which? Some layers built on top of JTAG monitor the state transitions, and use uncommon paths to trigger higher level operations.

Instruction register sizes tend to be small, perhaps four or seven bits wide. Two key instructions are:. This allows JTAG hosts to identify the size and, at least partially, contents of the scan chain to which they are connected. So the bits not written by the host can easily be mapped to TAPs.

It could for example identify an ARM Cortex-M3 based microcontroller, without specifying the microcontroller vendor or model; or a particular FPGA, but not how it has been programmed.

That way all TAPs except one expose a single bit data register, and values can be selectively shifted into or out of that one TAP's data register without affecting any other TAP. The IEEE Some of these instructions are "mandatory", but TAPs used for debug instead of boundary scan testing sometimes provide minimal or no support for these instructions.

Devices may define more instructions, and those definitions should be part of a BSDL file provided by the manufacturer. Devices communicate to the world via a set of input and output pins. By themselves, these pins provide limited visibility into the workings of the device. However, devices that support boundary scan contain a shift-register cell for each signal pin of the device. These registers are connected in a dedicated path around the device's boundary hence the name.

Pdf ieee 1149.1

The path creates a virtual access capability that circumvents the normal inputs and outputs, providing direct control of the device and detailed visibility for signals. Commercial test systems often cost several thousand dollars for a complete system, and include diagnostic options to pinpoint faults such as open circuits and shorts.

They may also offer schematic or layout viewers to depict the fault in a graphical manner. To enable boundary scanning, IC vendors add logic to each of their devices, including scan cells for each of the signal pins. These cells are then connected together to form the boundary scan shift register BSR , which is connected to a TAP controller. Overhead for this additional logic is minimal, and generally is well worth the price to enable efficient testing at the board level.

An example helps show the operation of JTAG in real systems. This is a non-trivial example, which is representative of a significant cross section of JTAG-enabled systems. Licensees of this core integrate it into chips, usually combining it with other TAPs as well as numerous peripherals and memory. Examples of such chips include:. Those processors are both intended for use in wireless handsets such as cell phones, which is part of the reason they include TAP controllers which modify the JTAG scan chain: Debugging low power operation requires accessing chips when they are largely powered off, and thus when not all TAPs are operational.