| 摘要 |
PURPOSE:To avoid erroneous discrimination by writing data and its complement in the first half and the latter of an area simultaneously and inverting contents of the first half or the latter read out at the check time and comparing contents of the first half and the latter with each other to discriminate normality or abnormality. CONSTITUTION:Data M1, M2... are written with complements M1', M2'... on addresses 80H, 81H... of a stand-by RAM. When this RAM is checked, data is read out by the start address 80H and is stored in an accumulator A, and contents of the accumulator A are copied to an accumulator B, and contents of the accumulator B are inverted. Normality is discriminated in case of A=B, but abnormality is discriminated in case of Anot equal to B. Thus, this checking method is not affected even if clocks are stopped during write to the RAM, and errone ous discrimination is avoided because the comparison between contents of the first half and the inverted value of contents of the latter results in disaccord even if the area is set to all '0' or '1' by a momentary break of power supply or the like. |
