| 摘要 |
PURPOSE:To improve the interchangeability of a position of an entry point, by providing a bit showing control information at every page unit of a main storage, and checking whether the execution control shift is normal or not. CONSTITUTION:A main storage 2 is divided into prescribed blocks called a page, and a branch control information bit corresponding to the page in the ratio of 1 to 1 is stored in a branch control information table 18. An instruction 5 is read out, is decoded in a code part 7, and when contents of a buffer register 6 are a branch instruction, an address of an instruction address register 1 is compared with an address of a branch address part 8 by a comparator 9. If its privilege level is equal, the branch instruction is executed through a signal line 14. If it is different, a branch validity checking part 16 is started by an output of a signal line 15. On the other hand, contents of the branch address part 8 are inputted to a table readout part 19, and page information to the branch destination address is checked by a checking part 20. When it is correct, a branch instruction is executed, and if it is an error, the error detection is outputted to a signal line 17. |
