| 摘要 |
PURPOSE:To improve the reliability of the whole operation by storing a bit, obtained by an exclusive OR operation an invert bit and a previous parity bit, and the inverted bit of a memory in a degeneration fault and by inverting them in readout operation. CONSTITUTION:For writing from a write data register WOR to a memory MM, an invert bit IB and a previous parity bit PB and exclusively ORed and the result is stored in the memory MM. When the contents of the memory MM are transferred to a read data register RDR, party checks on a data bit DB and a parity bit PB are made. In this case, when the stored position of the bit IB in the memory degenerates to 0 and the storage location of the bit PB degenerats to 0, the same value with the memory MM is stored in the register RDR because an inverting circuit does not operate. The parity check results in a parity error in this case and a defective invert bit is detected. |
