| 摘要 |
PURPOSE:To prevent a sequence program stored in a ROM from being illegally copied. CONSTITUTION:A program memory 2 is provided with a first memory 2a composed of a RAM and a second memory 2b composed of the ROM. In the case of transferring the sequence program from the first memory 2a to the second memory 2b, it is ciphered through a ciphering part 7 by using a cipher key set to a key setting part 9. In the case of transferring contents from the second memory 2b to the first memory 2a, they are deciphered through a deciphering part 8 by using a decipher key set to the key setting part 9. The cipher key and decipher key of the key setting part 9 are set by a supporting tool. |
