|
BSDL Validation smoothes the way for 1149.6
A semiconductor manufacturer that had developed a device which complied with the new IEEE 1149.6 Boundary-Scan Standard for Advanced Digital Networks recently took advantage of ASSET’s BSDL Silicon Validation service. The company’s reasoning was simple: Achieve a high level of adoption by ensuring a high level of customer satisfaction. Accurate, high-quality BSDL information describing the device’s boundary scan capabilities is an important ingredient in the market’s acceptance of a component.
 Advanced digital chip-to-chip interconnect networks that reach speeds in the one to 10 gigabits-per-second (Gb/s) neighborhood can not be structurally tested by standard IEEE 1149.1 boundary-scan methods because 1149.1 is limited to DC-coupled circuit board buses. Many of these advanced serial buses, such as Gigabit Ethernet, Fibre Channel and others are based on AC-coupled interconnects and/or differential signaling.
As a result, the 1149.6 standard was developed with 1149.1 as a foundation. Two years ago, ScanWorks was the first JTAG system to support the testing of 1149.6 devices, making ScanWorks at the time the only boundary-scan system that could test both DC-coupled buses with 1149.1 methods and the new high-speed AC-coupled nets with 1149.6 methods on the same printed circuit board.
Why Validate?
That semiconductor manufacturer had ASSET validate the 1149.1 and 1149.6 capabilities of its new device because it wanted to be certain that the device complied with the 1149.1 and 1149.6 standards, and that the BSDL file describing the chip’s embedded JTAG capabilities was completely accurate. Validating 1149.1 compliance and BSDL accuracy is a prerequisite for doing the same thing for 1149.6.
In many instances, the validation process can begin with the company submitting a device’s BSDL file to ASSET’s free web-based BSDL Validation Service. This service was jointly developed by ASSET and Agilent Technologies. It syntactically and semantically checks the submitted BSDL file, confirming correct spelling, punctuation, instruction codes, register associations and register cells that are required by the 1149.1 standard. It also automatically generates test patterns, creating a set of test vectors in a simple truth-table. These vectors can effectively test a chip design during the simulation phase to verify that it meets many of the requirements of the 1149.1 boundary-scan standard.
Once a chip manufacturer has sample silicon, it can take the validation process another step forward with ASSET’s BSDL Silicon Validation Service. Unlike the BSDL Validation Service which is limited to 1149.1 compliance, the BSDL Silicon Validation Service verifies the accuracy of 1149.1 and 1149.6 BSDL files against actual silicon. A sample device is sent to ASSET and placed in a fixture that provides proper power and ground, boundary scan access to each I/O, access to the boundary scan signals of TRST, TMS, TCK, TDI and TDO, and static control of compliance enable pins. Lastly, a test sequence is generated for the device to empirically validate that its embedded JTAG capabilities are described accurately in its BSDL file. This is performed for the device’s 1149.1 capabilities first and then for its 1149.6 infrastructure.
 The case of the chip manufacturer with the new 1149.6 device pointed out the value of the BSDL validation process. In this instance, several discrepancies were discovered between the chip’s boundary scan facilities and the way they were described in the BSDL file. Something as simple as an incorrectly described ID code register or clock signals that had been inadvertently swapped can cause significant problems later for circuit board designers and test engineers. Unfortunately, the errors may not become apparent until the board has been designed and a test strategy is being developed. At that point, changes in the board design to accommodate greater test coverage are costly indeed.
The chip manufacturer in this case was fortunate because several errors were identified by ASSET’s BSDL Validation Service and BSDL Silicon Validation Service. A simple fix to the BSDL file eliminated the chance of finding out about the inaccuracies later from a dissatisfied customer.
| 
