ALTERNATE MEMORY CHECK SYSTEM

PURPOSE:To check the alternate operation and alternate memory at a storage device having alternate memory effectively, by inverting control of write-in data for an arbitrary information bit. CONSTITUTION:A write-in information inverting circuit 15 is provided between a write-in information bus 1 and a normal memory 2, and connected to a write-in information inverting bit location storage register 17 with a write-in information inverting control line 18. The control of an alternate memory 7 is made by storing the alternate bit location information to an alternate memory bit location storage register 9 via a control line 20 externally, the write-in information inverting bit location information of the register 17 is given to a circuit 15 with a control line 18 to invert the information of the corresponding write-in information bits. Thus, the inverting control of an arbitrary write-in information bit can be made.