DIGITAL SCRAMBLING METHOD OF DATA AND ITS USE TO PROGRAMMABLE CIRCUIT

PROBLEM TO BE SOLVED: To improve the protection of data in a programmable circuit by discriminating instruction data of a program from other data at the time of generating an execution code and executing first substitution for instruction data or other data. SOLUTION: A first substitution circuit is DBr2 is arranged between RAM and a data bus DBUS and a second substitution circuit DBr3 is arranged between EEPROM and the data bus DBUS. Data stored in RAM and EEPROM are transferred on the data bus DBUS in a state where they are scramble- released. Namely, first substitution is special one executed at the time of generating the code and second substitution is that executed with the input of RAM. Thus, the protection of data in the programmable circuit can be improved.