| 摘要 |
PURPOSE:To ensure an error detection when a control memory is read out regarding an optional address, by writing with inversion the bit designated among the ECC codes produced from the ECC generating circuit into a control memory when a microinstruction is written into the control memory. CONSTITUTION:The control memory write data is set to the microinstruction register 120 when a microprogram is written into the control memory 100. Then the ECC code is produced at the error detection/correction circuit 200 for the write data mentioned above, and either this code bit or its reverse bit is selected by the selection gate 222 and by an indication given from the check bit reverse flag generating means 230 to be written into the memory 100 along with the control memory data. Both the control memory data and the ECC code including the reverse bit are read out in the read mode, and an error detection is given by the circuit 200. If the error detecting action is correct, are error is detected in the control data to which the ECC code including the reverse bit is added. In such way, the normal operation is confirmed easily for an error detection. |
