ATCA considers adding JTAG to standard
As members of the SJTAG working group, ASSET’s Adam Ley, Chief Technologist, and Dave Bonnett, Technical Marketing Manager, have been invited to offer their input on how the working group that is developing PICMG®’s Advanced Telecommunications Computing Architecture (AdvancedTCA®) specification might include JTAG as an option. According to Ley, there are similarities between the approaches that the SJTAG and ATCA working groups have considered.
 “Since ATCA is a system-level specification, the working group’s interest in JTAG as an optional feature has been initiated with a top/down or system-level approach,” Ley said. “Both ATCA and MicroTCA™ are deployed in telecommunications computing applications, so it makes sense that PICMG should think about including JTAG in ATCA for many of the same benefits for which it was adopted in MicroTCA. Having a defined option for JTAG in ATCA will give manufacturers and system integrators the core capabilities they need for a number of useful applications, such as remote management, testing and firmware updates.”
Because of the unique characteristics of ATCA, the working group will likely consider a JTAG architecture that is something of a departure from conventional system architectures, such as the multidrop or star (radial) TAP (Test Access Port) architectures.
ATCA specifies large form-factor cards and chassis for telecommunications application in the network infrastructure. As such, it is being implemented in next-generation carrier-grade communications equipment. The family of specifications that embodies ATCA incorporates the latest advancements in high-speed interconnect technologies, next-generation processors and improved reliability, manageability and serviceability.
PICMG’s MicroTCA is complementary to ATCA. MicroTCA blades conform to smaller form-factors with the intention of extending the horsepower of the ATCA fabric in the infrastructure to applications on the edge of the network.
An ATCA system, as specified by PICMG, is a fabric of boards or server blades installed in chassis slots and connected to each other by serializer/deserializer (serdes) links. The serdes signals are routed between chassis slots through one or two ATCA fabric switch blades, which are located at designated slots in the chassis. The boards or blades in an ATCA chassis are often configured with daughter cards that conform to another related standard, the Advanced Mezzanine Card (AdvancedMC™/ AMC) specification.
Any JTAG architecture ultimately chosen for ATCA will likely support hierarchical access to the boards or blades installed in the chassis as well as to the AMC daughter cards mounted on ATCA blades. This could necessitate local JTAG chain management on ATCA blades similar to the MicroTCA’s JTAG Switch Module. This type of local board-level configuration of JTAG could employ a programmable star architecture to each AMC on the ATCA blades.
Clearly, PICMG is considering adding JTAG as a defined option to ATCA because of the many long-term benefits boundary scan will deliver. No other technology can bring to advanced telecommunications and computing systems the capabilities that boundary scan does, including embedded remote testing, diagnostics, in-system programming, system-level management functionality and many others.
For Adam Ley’s article in Connect on the inclusion of JTAG as a defined option in MicroTCA, click here.
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