JPS6451536A - Output protector - Google Patents

Abstract

PURPOSE:To prevent the outputting of erroneous data to an equipment by adding an abnormality decision circuit which decides the presence/absence of an abnormality based on a decision result outputted from a pattern decision circuit and a write signal, and providing a gate not to output a write signal to an equipment in case of abnormality occurring. CONSTITUTION:In case data is transferred from a computer 1 to an equipment 2, the computer 1 executes an output instruction. During this time, a write signal WR and an address signal ADD representing the destination of the data are outputted from the computer 1 in addition to a data signal DAT. First, whether the pattern of the data signal DAT coincides with a preliminarily-set pattern or not is decided by the pattern decision circuit 3, and a decision result is outputted to the abnormality decision circuit 4. The decision as to abnormality/normality is executed based on said result and a write signal WR, and in case of normality being decided on, a signal is transmitted to the gate 5 to open the gate 5, and the write signal WR is outputted to the equipment 2. In case of abnormality, the signal WR necessarily is not outputted to the equipment 2.