Abstract: A memory data holding circuit for ensuring holding of the stored contents of a memory even if power happens to be turned OFF when the memory is being accessed. A first detecting circuit (2) detects the turning-OFF of the power supply, and a second detecting circuit (7) detects whether a memory (1) is being accessed or not. A switching circuit (8) supplies an operating current from a backup power supply (3) to the memory (1) only when the first detecting circuit (2) detects that the power supply has been turned OFF and the second detecting circuit (7) detects that the memory is not being accessed. An access inhibit means (5, 7) inhibits access to the memory (1) only when the first detecting circuit (2) detects that the power supply has been turned OFF and the second detecting circuit detects that the memory is not being accessed, so that access to the memory (1) is prevented being discontinued before access is completed.