| 摘要 |
PROBLEM TO BE SOLVED: To protect the destruction of file areas owing to the runaway of a user program and the like by allocating the respective divided sections of RAM in a program area and the file areas. SOLUTION: The address bus of CPU 2 and INHBIT 1-3 connect RAM 1 as the program area and RAM 2-8 as the file areas to RAM 8 constituted by eight blocks via a RAM bus 15 constituted by an AND circuit 13 and a RAM bus decoder 14. When a user program operates, INHIBIT 1-3 are set to '0' on OS, and the RAM 2-8 file areas except for RAM 1 where the user program is in the middle of operation are prevented from directly being accessed from the user program. Even if the user program runs away and CPU 1 executes the program for accessing RAM 2, only RAM 1 is accessed since the RAM bus 15 is connected to RAM 8. Thus, the file areas after RAM 2 are prevented from being destroyed. |
