WRITE PROTECTION SYSTEM FOR GENERAL-PURPOSE REGISTER

摘要

PURPOSE:To increase the processing speed together with reduction of the design quantity of both hardware and firmware and at the same time to prevent the wrong rewrite of the specific information by using a general-purpose register at the storing destination of the specific information concerning an entire system. CONSTITUTION:When a register write instruction is fetched to an instruction register 30 from a memory 20, a register write detecting/operating mechanism 41 is started. The mechanism 41 performs a write operation to a specific general-purpose register like a general-purpose register 11 as long as this register 11 is designated by the register write instruction and with only a specific general-purpose register write instruction like an instruction 21. Meanwhile the mechanism 41 cancels the write operation with a normal general-purpose register write instruction like an instruction 22. The designation is given to the mechanism 41 through a specific general-purpose register designating/canceling mechanism 50 so that the register 11 is defined as a specific general-purpose register.