| 摘要 |
PURPOSE:To decide whether accessing is allowed or not at a high speed by setting the address range of a storage device which is capable or incapable of accessing for every program different in execution level which is executed in time-division basis. CONSTITUTION:An address register 1 holds an address for accessing a control storage, and a program execution level deciding circuit 3 inputs an execution request signal 7 to determine the execution level of a program to be executed, and also transfers the result to an execution level register 4. Starting-point and ending-point registers 5 and 6 which determine the lower limit and upper limit of accessible addresses are selected according to the contents of the execution level register 4. A comparing circuit 2 compares the value Z of the address register 1 with the selected values of the starting-point and ending-point registers 5 and 6, i.e. Y and X, thereby outputting an access inhibition signal 8 when Z>Y or when Z<X. |
