| 摘要 |
PURPOSE:To execute the free change and the holding of the secret of the contents of a machine instruction executed by an CPU by providing an address control circuit, a logical synthesizing circuit, etc., and changing the value of a built-in RAM. CONSTITUTION:From a program counter 1 to an address control circuit 11, a bus line 16 is provided. Thus, a RAM 4 is individually accessed from an address pointer 2 by the input of a control signal inversion MODIFY through a circuit 11 and accessed from the counter 1 simultaneously with a ROM 3. The ROM 3 and the RAM 4 are connected by bus lines 15, 16 and 18, and through a logical synthesizing circuit 12, the output is logically synthesized. Either of the data read from the ROM 3 by the input of the signal inversion MODIFY or the logical synthesizing result is sent through a changing-over circuit 13 to a data bus 5 and stored into an instruction register 6. Thus, the contents of the machine instruction executed by a CPU can be freely changed and the secret can be held. |
