PURPOSE: To omit complicated control and the increase of hardware quantity and also to facilitate additions and changes of functions, by substituting the software for hardware processing using an operating board or a service processor, etc.
CONSTITUTION: A memory area 10 includes a store area 12 for a hardware processing substitute program which works at a program level (level X) exclusive for hardware processing in addition to an area 11 which stores an ordinary control program. An address exception is decided to inhibit access to the area 12 while a control program, i.e., a program excluding those having levels X is running. While the access is possible to all areas of a memory while a program having a level X is running. An external register group 15 consists of a group A13 and a group B14. The access is possible for the group A from the control program and the program of level X; while the access is possible for the group B from the program of level X only.
SATO MASAO
NISHIOKA JUNJI
