ALTERNATING-COMPLEMENTARY LOCATOR AND ITS USE FOR ERROR LOCATION IN DUAL-MODULAR REDUNDANCY WITH COMPARISON STRUCTURE

The dual-modular redundancy with comparison （DMRC） structure is a kind of widely used low-cost fault-tolerant structures. When a fault occurs in one of two redundant modules, the comparator gives an error-detecting indication signal. This indication output can be used as an interrupt signal to start an error handling procedure, or as a hardware signal to stop the operation or to start reconfiguration and recovery of the DMRC structure. However, the drawback of such a structure is that the comparator can not indicate the faulty redundant module. This will result in a great time overhead to error location and system reconfiguration. To diminish the time overhead of error location, a DMRC structure with concurrent error location capability is presented. Each output of a redundant module is an alternating variable. The two outputs produced by two redundant modules at the same time constitute an alternating-complementary variable. It is checked by an alternating-complementary locator. During normal operation, it can be determined whether a DMRC structure is error-free, or a redundant module or the locator itself is faulty or not according to the output given by the locator. The alternating-complementary locator is constructed by D-flip-flops and gate circuits. It is proved that it is totally fault locating. The concurrent error location capability of the proposed DMRC structure is built by the time redundancy principle, so it is suitable to be used in the non-speed-critical fault tolerant systems.