| 摘要 |
PURPOSE:To make improper program decoding by a third person impossible, by separately storing operational codes in an internal ROM and operands in an external memory. CONSTITUTION:When the storing content of an external memory 2 and internal ROM4 are as shown in the table, the data '00' of an address '1,000' are first read into an one-chip CPU from the external memory 2 by means of a program controller (PC) 1 and stored in a pointer 3 and, at the same time, the PC 1 is subjected to increment. The data stored in the pointer 3 are then utilized to designate one of operational codes of addresses '0'-'FF' written in the internal ROM4. Since the data are '00', the data '69' at the address '0' of the internal ROM4 are designated as an operational code and stored in an instruction register 5. After the storage, the operational code is interpreted as a byte instruction having an one-byte operand for setting immediate data in A-register by means of an instruction decoder 6. |
