How Military and Aerospace Systems Can Benefit from System Test Access Management (STAM) Using IEEE-P2654

Access to internal circuit nodes and elements from the system level improves test and diagnostic coverage. The traditional approach of tearing down a system in order to ascertain whether a subsystem, a circuit board or a component is in fact faulty is inefficient and often ineffective, causing no fault found (NFF) results. System test access management (STAM) working group efforts under IEEE-P2654 offers potential benefits. Because STAM provides optional means to communicate with internal access points, diagnostics can be improved. With more exact diagnoses of line replaceable units (LRUs) from the organizational level of repair (O-level), and better diagnoses of shop replaceable assemblies (SRAs) at the intermediate level of repair (I-level) a reduction in NFFs will reduce support costs. STAM, a subset of system level JTAG (SJTAG) enables access to boundary scan data through various interfaces, such as the Serial Peripheral Interface (SPI) [1] bus, the Inter-Integrated Circuit (I
²
C) [2] bus or the Universal Serial Bus (USB) bus. Military buses, such as the MIL-STD-1553, and avionics buses such as the ARINC 429 could also be incorporated into the STAM domain.