| 摘要 |
PURPOSE:To avoid a fixed fault of a control storage with a simple constitution, by providing an address line replacing circuit for mutual replacement of address lines. CONSTITUTION:A write address is supplied from a write control circuit 4 via a switch circuit 7 and an address replacing circuit 6. The read information which is read out by the circuit 4 and given from an external storage 17 is written to a control storage 1 for each bit. This bit information is read simultaneously out of the storage 1 and then compared with the write bit information through a comparator 3 after passing through a control storage register 2. If no coincidence is obtained from this comparison, a fault is discriminated for a memory cell corresponding to the storage 1. Then the circuit 6 is controlled by the circuit 4, an address line replacement mode register 5, etc. The address lines of the storage 1 are replaced with each other to perform the similar writing and the discrimination of a fault. In such a way, a fixed fault can be avoided for a control storage with a simple constitution excluding an error check code generating part, an error detecting/correcting part, etc. |
