When your board goes into manufacture, you need the advantages that XJTAG can give you. The Boundary Scan system is CPI's specialised run-time environment for manufacturing. It re-uses the tests from the design and prototyping stages and adds a range of extra features as well.
In one system, we have interconnect testing; in-system programming, serial number handling and configurable log files for your audit trail. No more accessibility problems with fine-pitch or BGA devices - you can now move on from inconclusive X-ray inspections and instead be certain that the devices are free from opens and shorts, including direct inspection of the signals.
Using just the JTAG test access port (TAP), you can program not only the JTAG devices on the board, but Flash memory and configuration ROMs as well. To track down intermittent faults, you can repeatedly loop tests until the failure occurs. Advanced serial number handling and configurable log files give you easy control over of the state of your production processes.
XJTAG Advanced Connection Test
A connection, or interconnect test is a vital part of any testing suite, checking that components are properly soldered onto the board and that there are no short circuits.
Improved Connection Testing
The XJTAG connection test detects PCB faults in three categories; short circuit, open circuit and stuck-at faults. While these are the same categories of faults that are identified by other connection tests, XJTAG is able to identify more faults and indicate their positions more precisely.
ATPG "On the fly"
The XJTAG connection test generates its test patterns each time it is run, so any design modifications to the board can be quickly and easily incorporated without the need to have a new set of tests developed by your connection test vendor.
Test Beyond Resistors
This diagram shows a situation that causes a major problem for many JTAG connection tests. While the conflicting algorithm, used by many traditional connection tests, is able to identify the short circuit between nets C and D, the inline resistors in nets A and B mean that the short circuit between those two nets would not be detected. The XJTAG connection test algorithm overcomes this problem.
In-System Programming
Many modern programmable devices, such as FPGAs, DSPs and CPLDs, are not just designed to be JTAG compliant, but also include additional JTAG functionality, allowing them to be programmed after they have been attached to the circuit. Other devices, such as some flash memories, or non-JTAG versions of the above, can be programmed indirectly through their connection to devices in the JTAG chain. The ability to use JTAG to program devices 'in system' avoids the need to buy expensive programmers and socketed devices. There is also the advantage of being able to easily update the image held on the device.
|
