PORTABLE PROCESSOR

PURPOSE:To surely protect data stored in a memory card from being written at the time of CPU runaway in a portable processor such as handy terminal for storing data in a memory card. CONSTITUTION:The. portable processor includes a CPU 12 for executing write access to a memory space arranged on a memory card 10, a means 14 for determining an address range allowing an access from the CPU 12 to the card 10, a protection control register 16 for writing the determined address range prior to the write access to the card 10, an address comparator 18 for comparing the address of the write access from the CPU 12 to the card 10 with the address range written in the register 16, a write control circuit 20 for allowing the write access of the CPU 12, and a writing means 22 for writing a write access inhibiting address range in the card 10.