Comparison of system test alternatives using industry boundary scan standards

High fault coverage embedded system test is a desirable capability in many applications. The test requirement may be for on-line test, remote test capability or for rapid field diagnostics and repair. Two industry standards have recently become available for this purpose. The serial 4 wire IEEE 1149.1 boundary scan standard is widely used for board test and provides interconnect test and device functionality. Although primarily intended as an aid to prototype and manufacturing test, 1149.1 can also be extended over the backplane by the use of commercially available hardware. The proposed IEEE P1149.5 standard is modeled on the DOD's TM bus and is a fault tolerant, 5-wire, packet based master-slave communications protocol for up to 251 modules. This paper discusses the relative merits of various techniques extending 1149.1 over a backplane. The alternatives are evaluated in terms of test capability and efficiency, fault tolerance and board real estate and component overhead.