| 摘要 |
<p>PURPOSE:To eliminate the need of a peripheral equipment for preventing read- out by providing a switch for storing a programmable cipher code for deciding whether read-out of storage data is appropriate or not. CONSTITUTION:In the case of executing read-out, when a read-out application input code signal is inputted from an address bus 9, and also, this input code signal is latched to a latch circuit 7 by controlling a latch control 8, a compara tor 5 compares it with a cipher code stored in a mask ROM 3 output through a cipher code bus 4. When both of the coincide with each other, a switch control 10 is activated, a switch circuit 11 is made in an ON-state, and address informa tion of the address bus 9 is transferred to a main memory 13. In the case the input code signal and the cipher do not coincide with each other, the switch circuit 11 remains cut-off, and by an address signal, storage data of a main memory 13 is not output normally. In such a way, a peripheral equipment for preventing read-out becomes unnecessary.</p> |
